Augusta is the capital of the U.S. state of Maine and the county seat of and most populous city in Kennebec County. The city's population was 18,899 at the 2020 census, making it the 12th most populous city in Maine, and 3rd least populous state capital in the United States after Montpelier, Vermont, and Pierre, South Dakota. The area was explored in 1607 by English settlers from the Popham Colony at the mouth of the Kennebec River.