Newburg is a former census-designated place in Jefferson County, Kentucky, United States. The population was 20,636 at the 2000 census. On January 6, 2003, the area was annexed to the city of Louisville due to a merger between the city and Jefferson County's unincorporated communities. Newburg is now thought to be a neighborhood within th…Newburg is a former census-designated place in Jefferson County, Kentucky, United States. The population was 20,636 at the 2000 census. On January 6, 2003, the area was annexed to the city of Louisville due to a merger between the city and Jefferson County's unincorporated communities. Newburg is now thought to be a neighborhood within the now merged city of Louisville.