Tres Alamos

Overview

A river crossing before Benson

Tres Alamos was a farming settlement and stage stop on the San Pedro River, north of Benson. The 1945 USGS Happy Valley sheet marks its site on the west bank, near the mouth of Tres Alamos Wash. The calculated drive from Benson is about ten miles, though access to the final mile has not been confirmed.

Anglo and Mexican families filed claims here in December 1865 and dug an irrigation ditch, according to Harry E. O'Neil's 2005 history in the Cochise County Historical Journal. Apache raids killed settlers from 1867 on. Wikipedia says the settlers abandoned the area after a few years; O'Neil says they stayed, and a count in June 1875 found 203 people. In 1875 and 1876, he writes, Tres Alamos had a post office, a stage station, a hotel, several merchants, a military telegraph, two doctors and a school. Billy Ohnesorgen, who ran a stage stop on the river, later remembered that the first settlers, a colony of 25 Americans, "were all killed in time." Historian John D. Rose puts Ohnesorgen's station at the mouth of Tres Alamos Wash; O'Neil puts it at the Middle Crossing, near today's Benson.

The railroad shifted traffic south. The Southern Pacific reached the San Pedro in 1880 and Benson grew up beside it. A new stage road bypassed Tres Alamos, and the post office closed in 1886. A few farmers and ranchers stayed on, and by 1945 the USGS map simply marked the "Site of Tres Alamos." In 2005 O'Neil found ranches, small farms and homes along the valley, and adobe ruins reduced to mounds of earth. Aerial imagery shows farm fields and a grid of roads on the west bank.

Timeline

Farms, stages and the railroad

1. Dec 1865Anglo and Mexican families file claims on Tres Alamos land and start an irrigation ditch, by Harry E. O'Neil's 2005 history. A special census in 1866 counts 59 people in the vicinity.
2. About 1871Billy Ohnesorgen starts running a stage stop on the San Pedro, about three years after reaching Arizona in February 1868, by John D. Rose's account. Rose puts it at the mouth of Tres Alamos Wash; O'Neil puts it at the Middle Crossing near today's Benson. Wikipedia places Ohnesorgen at Tres Alamos in 1865.
3. 1874The Tres Alamos post office opens. O'Neil says John Montgomery ran it the first year and Thomas Dunbar from August 1875.
4. Jun 1875A count by Henry Clay Hooker and a Colonel Hodge finds 100 men, 47 women and 56 children, O'Neil writes.
5. Winter 1878–79Thomas Dunbar petitions the Pima County supervisors for a bridge at Tres Alamos in November 1878. That winter Ohnesorgen builds his own toll bridge at his station, with a 25-foot span, Rose writes.
6. Sep 15, 1879Ohnesorgen and H.C. Walker form the Ohnesorgen & Walker stage line.
7. 1880The Southern Pacific arrives and Benson is founded to the south. Wikipedia says a new stage road built by J.D. Kinnear bypassed Tres Alamos, and the stage stop was abandoned.
8. Sep 1886The post office closes. Farmers and ranchers stay on in the valley, O'Neil writes.
9. Jun 23, 1941Carr Tuthill's Amerind Foundation report on the archaeological Tres Alamos site, across the river on the east bank, goes to the Smithsonian with a letter of this date.
10. 1945The USGS Happy Valley sheet marks the "Site of Tres Alamos" on the west bank, with "Indian Ruins" across the river.
11. 1958The same sheet, revised, names Tres Alamos Ranch just south of the old site.
12. 2005The Cochise County Historical Journal describes the few remaining adobe ruins, east of the river, as little more than mounds of earth, and two grave sites as on private land and off limits.
13. Oct 2026BLM's Surface Management Agency layer classifies this page's point as Private or Unknown. The layer does not establish ownership or a right of access. We found no newer dated report on the site.

Stage stop

Ohnesorgen's station and bridge

Historian John D. Rose pieced together the station's story from Billy Ohnesorgen's own recollections and the newspapers of the day. Ohnesorgen reached Arizona in February 1868 and worked in Tucson. About three years later his brother bought an isolated stage stop, which Rose places at the confluence of Tres Alamos Wash and the San Pedro, and asked Billy to run it. Wikipedia dates his arrival at Tres Alamos to 1865, so the sources disagree by about six years. Wikipedia also says Tucson presidio soldiers farmed here in 1768, but the Presidio Museum dates the presidio's establishment to 1775, so that claim cannot be right as written. O'Neil's history puts presidio-escorted farming at Tres Alamos in the early 1800s. We could not independently confirm that the article's 1830 settlement and 1860 Soza ranch dates refer to this townsite.

Where Ohnesorgen's station stood is disputed. Harry E. O'Neil's 2005 history calls Tres Alamos the Lower Crossing of the San Pedro and puts Ohnesorgen's station at the Middle Crossing, near today's Benson. John Vosburg, a partner of Tombstone's discoverers quoted by Rose, also remembered finding Ohnesorgen at the San Pedro crossing "where the Town of Benson now is," and said the stage line crossed the river at Tres Alamos. O'Neil names Thomas Dunbar as the Tres Alamos station keeper, and its postmaster from August 1875 until the office closed in September 1886. The account below follows Rose.

The station was adobe, with walls 18 inches thick, and the government kept a picket of eight or ten soldiers there. Ohnesorgen said Apaches never attacked it while he was there, though they had killed two soldiers there before he came. In November 1878 Dunbar, who ran a competing stage stop, asked Pima County to build a bridge at Tres Alamos. That winter Ohnesorgen built his own wooden toll bridge, with a 25-foot span, and charged tolls. He advertised that tolls would repay his costs, but Rose notes that he kept charging after apparently recovering them. In one high-water month, he said, he took in $400. On September 15, 1879, he went into partnership with H.C. Walker in the Ohnesorgen & Walker stage line. Summer storms damaged the bridge in 1880.

"Stage coaches could never compete with the arrival of railroads." John D. Rose, on Tres Alamos

That same year the Southern Pacific built through the valley and Benson was founded. Wikipedia adds that J.D. Kinnear built a new stage road that skipped Tres Alamos, and the stop was abandoned. Wikipedia's article also places the town at the east end of Redington Pass, but its own coordinates and the USGS maps put it on the San Pedro just north of Benson.

The site today

Where Tres Alamos stood

The newest dated description of the site is Harry E. O'Neil's, in the Fall/Winter 2005 Cochise County Historical Journal. He found the valley dominated by ranches, small farms and homes. The few remaining adobe ruins, he wrote, are spread over several acres on the east side of the river and have been reduced to little more than mounds of earth. He noted numerous pieces of purple glass, old tin cans and other odds and ends, and two major grave sites, both on private land and off limits. An undated listing records no remains. We found no newer report.

Two points mark the townsite on maps. The 1945 USGS Happy Valley sheet prints "Site of Tres Alamos" on the west bank of the San Pedro, in section 6, between the mouth of Ash Creek to the north and the mouth of Tres Alamos Wash on the opposite bank to the southeast. That is the point this page uses. GNIS, and Wikipedia with it, gives a point about half a mile southwest named Tres Alamos Ranch. The 1958 revision of the same sheet shows that ranch, with a few buildings and wells, just south of the old site.

Across the river, the 1945 sheet marks "Indian Ruins" in section 5. That is consistent with the archaeological Tres Alamos site, which the Smithsonian's record of Carr Tuthill's Amerind Foundation report places on the east bank in section 5, T16S R20E. The same record calls it about fifteen miles north of Benson, which doesn't match the map. The 1973 sheet no longer names Tres Alamos. It shows Willow Lake and a grid of subdivision roads to the southwest of the site.

• Adobe ruins reduced to mounds of earth, east of the river (2005 report)
• Two grave sites on private land, off limits (2005 report)
• Townsite marked on the west bank in 1945
• "Indian Ruins" marked across the river on that map

Historic maps

Tres Alamos on USGS maps, 1945–1973

Crops from the USGS Historical Topographic Map Collection, centered on the townsite. Each sheet shows what surveyors mapped that year; compare them with today's topo and aerial on this page.

19451:62,50019581:62,50019731:24,000

Map & directions

Getting there

Benson is the closest town. From Tucson, take I-10 east and leave it at the Ocotillo exit before Benson. Both calculated routes follow North Ocotillo Road north, then about a mile of unnamed service roads. The destination is the 1945 townsite point on the west bank, classified Private or Unknown on BLM's map. The 2005 report puts the remaining adobe mounds across the river, on the east side. These routes show a possible road connection, not confirmed public access. We haven't driven them and couldn't verify permission to use the last stretch.

Base map: USGS The National Map (public domain). Routes: OSRM on © OpenStreetMap contributors data (ODbL), computed October 2026. Times assume dry roads.

Photos

Have photos of Tres Alamos?

We haven’t added more photographs of Tres Alamos yet. If you’ve visited, share your photos and a field report below.

Visitor reports

Been to Tres Alamos?

Been there lately? Tell the next visitor what you found: whether you could get in, the state of the road and what's still standing. Photos are welcome. We read every report before it appears here.

Thanks. Your report reached us, and we'll read it before it goes on the page.

Farm and ranch

More farm and ranch ghost towns

The nearest in Arizona.

Guide

Cascabel

32.29, -110.38

Cochise County, Arizona

A ranching settlement on the lower San Pedro River that lost its post office in 1936 but never lost its people. Its name, by the standard account…

Living communityFarm and ranch

Guide

Redington

32.43, -110.49

Pima County, Arizona

A ranching settlement founded in 1875 on the San Pedro River, with a store, a post office and a school. What's left lies inside a working family…

Ranch communityFarm and ranch

All 114 farm and ranch ghost towns →

Nearby

Other sites near Tres Alamos

Straight-line distance from the townsite to other mapped sites in our Arizona index.

• Pantano14.8 mi W · Pima
• Cascabel15.7 mi N · Cochise
• Johnson16.2 mi E · Cochise
• Total Wreck19.0 mi SW · Pima
• Contention City22.1 mi S · Cochise
• Cochise24.7 mi E · Cochise
• Fairbank25.3 mi S · Cochise
• Redington26.5 mi N · Pima

Sources

Sources and credits

1. ghosttowns.com, "Tres Alamos": fact sheet fields (roads, legal description, climate, best time, remains, post office dates) and its note placing the site on the Pomerene Road.
2. Harry E. O'Neil, "Tres Alamos: A Place Forgotten," Cochise County Historical Journal 35, no. 2 (Fall/Winter 2005), Cochise County Historical Society, read October 22, 2026: the December 1865 claims, the 1866 census and June 1875 count, the town in 1875–76, the post office keepers and closing month, Ohnesorgen's station at the Middle Crossing, Dunbar's station at Tres Alamos, early-1800s presidio-escorted farming, and the site in 2005 (adobe ruins reduced to mounds east of the river; two grave sites on private land and off limits). The newest dated report on the site.
3. Wikipedia, "Tres Alamos, Arizona", read October 20, 2026: the Kinnear road, post office dates, its 1874 founding date, the settlers leaving after a few years, and the separate Tres Alamos Ranch point (GNIS 22260). Its early history and location contain conflicts discussed above; its 1768 presidio claim is rejected.
4. Tucson Presidio Museum, "The Original Presidio San Agustín del Tucson": establishment on August 20, 1775, contradicting Wikipedia's 1768 claim.
5. John D. Rose, "Billy Ohnesorgen & Tres Alamos A.T.," Wyatt Earp Explorers, drawing on his book On the Road to Tombstone (2012): the station at the confluence, its adobe walls, the soldier picket, Ohnesorgen's arrival, Dunbar's 1878 bridge petition, the toll bridge, the Ohnesorgen & Walker line, the 25 first settlers, and John Vosburg's recollection of Ohnesorgen at the crossing where Benson now is.
6. Smithsonian National Anthropological Archives, MS 4106-a, Carr Tuthill, "Report on Tres Alamos" (submitted with a letter dated June 23, 1941; the report itself is undated): the archaeological site on the east bank, section 5, T16S R20E.
7. Wikipedia, "Tres Alamos Wash", retrieved October 2026: the wash meeting the San Pedro across the river from the former settlement.
8. USGS Historical Topographic Map Collection catalogue, queried October 20, 2026, and the map crops inspected: Happy Valley 1945 and 1958 (1:62,500), Galleta Flat East 1973 (1:24,000). The first marks the townsite; the later sheets show the ranch and changed roads.
9. BLM, Surface Management Agency layer, point query October 20, 2026: PVT, shown in the legend as "Private or Unknown." The service explicitly does not establish ownership boundaries; it does not confirm public access.
10. USGS 3DEP elevation query, October 20, 2026: 3,421.46 ft at the mapped townsite, rounded to about 3,420 ft.
11. OpenStreetMap road data, read October 20, 2026: North Ocotillo Road way 717597698 (edited October 4, 2025) and unnamed service ways 16789827, 810375862 and 810375863 (June 1, 2020). Surface tags do not establish current conditions or access. Routes: OSRM on OpenStreetMap data, October 2026; not field-checked.

Photo and map credits

• The 1945 USGS sheet marks the "Site of Tres Alamos" west of the San Pedro, with "Indian Ruins" across the river: U.S. Geological Survey, USGS catalog, Public domain
• Area base map, topo and aerial imagery: USGS The National Map (public domain).
• Historic maps: USGS Historical Topographic Map Collection (public domain): Happy Valley 1945, 1:62,500; Happy Valley 1958, 1:62,500; Galleta Flat East 1973, 1:24,000.