How many years did Democrats control Congress?

Since the Democratic Party first controlled both houses in 1837 under the 25th Congress, it has held control of both houses for over 75 years under 35 Congresses, according to both the House and Senate websites. As of 2015, the 114th Congress is controlled by the Republican Party.

Starting in the 20th century, the Democratic Party controlled 28 Congresses, 20 of which operated under a president of the opposite party. As of January 2015, the Democratic Party controls 7 state legislatures, Republican Party controls 24 and the remaining 19 states are divided. Furthermore, Nebraska is the only state to have a one-house, non-partisan legislature, as stated by the Washington Post.