<human>:  In the 1921 Irish general election, where did the Sinn Fein party win the most seats?
<bot>: The Sinn Fein party won the most seats in the Irish Free State, which was the name of the Irish state before it was partitioned into Northern Ireland and the Republic of Ireland. The Free State was formed in 1922 after the Irish War of Independence, which was a civil war fought between the Irish Republican Army and the British Army.