Kelseyville is a census-designated place (CDP) in Lake County, California, United States. Kelseyville is located 6 miles (9.7 km) southeast of Lakeport, at an elevation of 1384 feet (422 m). The place was originally called Kelsey Town in honor of Andrew Kelsey, the first American settler in Lake County. He was killed in 1850 in an uprising against him by the Pomo in 1849, that ended with the Bloody Island Massacre. The first blacksmith's opened in 1857. The place was called Uncle Sam after Mount Uncle Sam (now Mount Konocti). The Uncle Sam post office opened in 1858 and changed its name to Kelseyville in 1882.