La Grange is a home rule-class city in Oldham County, Kentucky, in the United States. The population was 10,067 at the time of the 2020 U.S. census. It is the seat of its county. An unusual feature of L…La Grange is a home rule-class city in Oldham County, Kentucky, in the United States. The population was 10,067 at the time of the 2020 U.S. census. It is the seat of its county. An unusual feature of La Grange is the CSX Transportation street-running mainline track on Main Street.