Hilmar (formerly, Hillmar) is an unincorporated community in Merced County, California. It is located 4.25 miles (6.8 km) west-southwest of Delhi, at an elevation of 92 feet (28 m). For census purposes, Hilmar is aggregated with nearby communities into the census-designated place Hilmar-Irwin, California. Hilmar began as a colony of Swedish immigrants in 1917. The first post office opened in 1920. Hilmar was the southernmost station of the Tidewater Southern Railway. The line terminating in the town was considered the mainline of the railroad and was projected to continue south toward Fresno or Bakersfield until the mid 1930s. The line into Hilmar was abandoned in the late 1950s.