Fort Atkinson is a city in Winneshiek County, Iowa, United States. The population was 349 at the 2010 census. It is home to the historic Fort Atkinson State Preserve and hosts a large annual fur-trapper rendezvous each September. Fort Atkinson holds the largest regional hay auction every Wednesday. Fort Atkinson was built to protect the Ho-Chunk (Winnebago) during their removal from Wisconsin. The name honors Henry Atkinson, the commanding officer in charge of the effort. Construction began in May 1840 and was complete by the summer of 1842. The regular army turned the fort over to Iowa volunteers as the troops stationed there were needed for the Mexican-American War. After the Ho-Chunk were removed from Iowa the post was abandoned on February 14, 1849. Fort Atkinson is located at 43°8′39″N 91°56′5″W / 43.14417°N 91.93472°W / 43.14417; -91.93472 (43.144034, -91.934839). According to the United States Census Bureau, the city has a total area of 0.31 square miles (0.81 km²), all of it land. As of the census of 2010, there were 349 people, 160 households, and 102 families residing in the town. The population density was 1115 people per square mile (430.5/km²).