Koerth is on Farm Road 531 three miles west of U.S. Highway 77 in south central Lavaca County. The families of William Ryan, Bernard O'Dougherty, and other settlers of Irish descent first settled the area in 1833. The original community was known as Yellow Bank, for Yellow Bank Creek, and Antioch. St. John the Baptist Catholic Church and school were built there by 1865, replacing a private school taught by Rube Walton in the H. P. Riley home. After the Civil War German and Czech immigrants began to replace the earlier settlers, and Charles G. Koerth built a store and became postmaster on May 19, 1879. The community took his name, as did the post office, which operated in his store from 1884 to 1887 and again from 1893 to 1910. By 1896 the community had a flour mill and gin. In 1914 a public school was built at the intersection of the old Victoria-Hallettsville and the Sweet Home-Hope roads. When the schools were consolidated in the 1950s students began attending classes in Sweet Home, and at the same time U.S. 77 was built along the east flank of the community. The population of Koerth from the early 1930s to about 1945 was twenty; the settlement had one business. In 1950 one store served a population of thirty. In 1990 the store remained, and the church was the center of community life for the population of forty-five. The population remained the same in 2000.