The 19th century and early 20th century saw the rise of Irish Nationalism, especially among the Catholic population. From the General Election of 1874 until the creation of the Irish Free State in 1922, the majority of MPs elected from Irish constituencies supported Home Rule, sometimes finding themselves holding the balance of power in the House of Commons. Frustrated by lack of political progress, an armed rebellion took place with the Easter Rising of 1916. Two years later, the more radical, republican party, Sinn Féin, won 73 of the 103 Irish constituencies. Sinn Féin had promised not to sit in the UK Parliament but rather to set up an Irish Parliament, known as the First Dáil, which declared Irish independence by reaffirming the 1916 declaration, leading to the subsequent Irish War of Independence. In 1921, a treaty was concluded between the British Government and a delegation of Irish leaders. Under the treaty, Northern Ireland would form a home rule state within the new Irish Free State unless it opted out. Northern Ireland had a majority Protestant population and opted out as expected. A Boundary Commission was set up to decide on the border between the two Irish states, though it was subsequently abandoned after it recommended only minor adjustments to the border.