Union is a city in Union County, Oregon, United States. The population was 1,926 at the 2000 census.
Union was platted on November 11, 1864 along the Oregon Trail. The name references the Union states, or Northern States, of the American Civil War.
La Grande was named the county seat when Union County was created in 1865. Due to the Thomas and Ruckle Road going through Union, it elected the county seat in 1872, but when the railroad was built it was put through La Grande instead of Union. La Grande became the bigger town within the county and regained the county seat in 1902. J. W. Shelton, a local attorney, chartered the Union Electric Power and Light Company in March 1890 to bring the railroad from Union Junction (2.5 miles away) to Union itself. The company was renamed the Union Railway Company in July 1890, and the rail spur was built into Union by August 1892. Shelton planned to build more lines, had a fight with his company partners (the Hutchinsons), then two competing firms were formed: Shelton's The Union Railway in January 1893, and Hutchinsons' Union Street Railway and Suburban Railway. Both companies competed to buy the Union Railway Company. Shelton maintained control until August 1905, when The Union Railway was renamed to the Union, Cove and Valley Railway. This company was bought the following year by a timber company from the East Coast.