Sourdough

The Schoolhouse That Left Sourdough Creek

A Name on the Federal Map

Sourdough, Montana, is a place that survives mainly as a label. The U.S. Geological Survey lists it as a populated place in Sweet Grass County, on the Ryan Creek quadrangle, and the agency's name index for the county includes both "Ryan Creek" and "Sourdough School" among its map names ("Sweet Grass"). The Sweet Grass County MTGenWeb project, a volunteer genealogical and historical site that draws on federal place-name data, places Sourdough about five miles northeast of Big Timber on Ryan Creek and says only that it "at one time had a school" ("Sweet Grass County History"). That is the entire official entry. It is a short record for a place that left no larger documentary trail.

The Setting

Sweet Grass County was organized in 1895 from parts of Meagher, Park, and Yellowstone counties (Sweet Grass County Growth Policy; "Sweet Grass County History"). Its northern and eastern portions became agricultural country, given over mostly to cattle, sheep, and dryland crops ("Sweet Grass County History"). A 2019 conservation plan prepared for the county likewise notes that farming concentrated in the northeast, where Sourdough sits (Sweet Grass County Long-Range Plan). The federal homestead laws of the period, including the Enlarged Homestead Act of 1909, which offered 320 acres, and the Three-Year Homestead Act of 1912, which shortened the residency requirement, encouraged settlement across Montana (Sweet Grass County Growth Policy). None of the sources consulted ties Sourdough's school to these laws, so any connection remains an inference rather than a documented fact.

The Schoolhouse

The one concrete artifact is the building itself. A one-room schoolhouse built in 1912 stood on Sourdough Creek, and in 1999 the Nevin family donated it to the Crazy Mountain Museum in Big Timber, where it was moved (Fence Post). The museum's current website lists the "Sourdough schoolhouse" among its principal exhibits, beside a replica Norwegian stabbur, a tipi, and the Fjare homestead cabin (Crazy Mountain Museum). The Billings Gazette, reporting on the museum, confirms that the schoolhouse originally stood on Sourdough Creek north of Big Timber (Iverson). The Fence Post adds that the museum keeps an extensive history of the county's schoolhouses and a wall of photographs of most of them.

An account quoting the museum's own school history gives the same construction date and identifies the site as the property of David Nevin, in what became School District 43. That detail comes from a single secondhand source and I could not confirm it on the museum's page, so I treat it as unverified.

Where Was Sourdough?

The sources disagree on location, and the disagreement should be stated plainly. MTGenWeb places the community about five miles northeast of Big Timber. The Fence Post and the Gazette place the schoolhouse about sixteen miles north of town. A straight-line measurement from the coordinates the USGS lists for Sourdough suggests a distance nearer eight miles. The differences may reflect road mileage against straight-line distance, or the possibility that the community and the schoolhouse site were not identical. Two creeks complicate the matter further: the USGS names both a Ryan Creek and a Sourdough Creek on the same quadrangle, and a ranch listing for the area refers to both flowing through one property ("Sweet Grass River Ranch"). The record does not resolve the question.

What the Record Does Not Say

The sources I could verify do not explain why the place or creek was named Sourdough, who lived there, how many pupils the school served, when it closed, or when the community dispersed. They do not document a post office, a store, or any business. Descriptions of Sourdough as a village or ghost town appear in tertiary sources but not in the archival or local historical material I could examine, and I have not repeated them. A fuller history would likely require the Crazy Mountain Museum's school files, Sweet Grass County school district records, or federal land patents for the surrounding sections, none of which were accessible online.

Works Cited

Crazy Mountain Museum. Home page. Crazy Mountain Museum, www.crazymountainmuseum.com/. Accessed 20 Oct. 2026.

The Fence Post. "Crazy Mountain Museum." The Fence Post, www.thefencepost.com/news/crazy-mountain-museum/. Accessed 20 Oct. 2026.

Iverson, Jake. "The Crazy Mountain Museum Tells Tales of Sweet Grass County's Vanishing History." Billings Gazette, billingsgazette.com/entertainment/the-crazy-mountain-museum-tells-tales-of-sweet-grass-countys-vanishing-history/article_1323cf26-2335-11ed-a8ff-ebc8e6e3ca0f.html. Accessed 20 Oct. 2026.

Sweet Grass County. Sweet Grass County 2014-2020 Growth Policy. Sweet Grass County, Montana, sgcountymt.gov/wp-content/uploads/2018/06/Final-Growth-Policy-publication-2014-2020.pdf. Accessed 20 Oct. 2026.

"Sweet Grass County History." Sweet Grass County MTGenWeb, sites.rootsweb.com/~mtsweetg/sgchgp.htm. Accessed 20 Oct. 2026.

Sweet Grass County Conservation District. Sweet Grass County Long-Range Plan. Natural Resources Conservation Service, Dec. 2019, www.nrcs.usda.gov/sites/default/files/2022-09/SweetGrassCounty-Montana-LongRangePlan-2019.pdf. Accessed 20 Oct. 2026.

"Sweet Grass." USGS Thesaurus, U.S. Geological Survey, apps.usgs.gov/thesaurus/term-simple.php?thcode=1&code=f30097. Accessed 20 Oct. 2026.

"Sweet Grass River Ranch, Big Timber, MT." Western Agri Financial, www.westernagrifinancial.com/properties/sweet-grass-river-ranch-big-timber-mt/. Accessed 20 Oct. 2026.