15th United States Congress  The Fifteenth United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met in the Old Brick Capitol in Washington, D.C. from March 4, 1817, to March 4, 1819, during the first two years of James Monroe's presidency. The apportionment of seats in the House of Representatives was based on the Third Census of the United States in 1810. Both chambers had a Democratic-Republican majority. The count below identifies party affiliations at the beginning of the first session of this congress. Changes resulting from subsequent replacements are shown below in the "Changes in membership" section. During this congress, two Senate seats were added for each of the new states of Mississippi and Illinois. During this congress, one House seat was added for each of the new states of Mississippi and Illinois. This list is arranged by chamber, then by state. Senators are listed by class and Representatives are listed by district. Senators were elected by the state legislatures every two years, with one-third beginning new six-year terms with each Congress. Preceding the names in the list below are Senate class numbers, which indicate the cycle of their election. In this Congress, Class 1 meant their term began in the last Congress, requiring re-election in 1820; Class 2 meant their term began with this Congress, requiring re-election in 1822; and Class 3 meant their term ended with this Congress, requiring re-election in 1818. The names of members of the House of Representatives are preceded by their district numbers. All representatives were elected statewide on a general ticket. Both representatives were elected statewide on a general ticket. All representatives were elected statewide on a general ticket. The 5th district was a plural district with two representatives. All representatives were elected statewide on a general ticket. All representatives were elected statewide on a general ticket. There were six plural districts, the 1st, 2nd, 12th, 15th, 20th & 21st, each had two representatives. There were six plural districts, the 2nd, 3rd, 5th, 6th & 10th had two representatives each, the 1st had four representatives. Both representatives were elected statewide on a general ticket. All representatives were elected statewide on a general ticket. The count below reflects changes from the beginning of the first session of this Congress. Lists of committees and their party leaders.