Farmers Union Gin Company, Cotton gin industrial complex in San Marcos, Texas.

Farmers Union Gin Company is a cotton gin complex at 120 Grove Street in San Marcos, Texas. Its present building went up in 1911, replacing an earlier structure destroyed by fire. The company ran San Marcos' largest industrial facility of its time until ginning stopped in 1966; the site is now a Recorded Texas Historic Landmark and listed on the National Register of Historic Places.

In 1908 Henry Kellerman, J. H. Barbee, A. H. Fleming, I. B. Rylander and J. H. Williams bought the premises at 120 Grove Street, and in 1909 they founded the Farmers Union Gin Company under Oscar Calvin Smith Sr. The gin ran until 1966, and the present building dates from 1911, replacing one destroyed by fire.

The company was established in 1909 under Oscar Calvin Smith Sr., a Texas Cotton Ginners Association organizer who served as San Marcos city commissioner from 1924 to 1941 and mayor in 1941–1942. The gin ran until 1966, and the site is now recognized by the Texas Historical Commission and the National Register of Historic Places.

The building stands at 120 Grove Street in San Marcos, Texas, and is listed on the National Register of Historic Places and as a Recorded Texas Historic Landmark. The sources describe no public tours, opening hours or interior access, so visitors should treat it as an exterior landmark viewed from the street.

The company took its name from the Farmers' Union, and its first president was Oscar Calvin Smith Sr. (1876–1948), a Texas Cotton Ginners Association organizer who served as San Marcos city commissioner from 1924 to 1941 and mayor in 1941–1942. The 1911 building replaced an earlier structure lost to fire.