State legislature (United States)

A state legislature in the United States is the legislature of any of the 50 U.S. states.
What is in them.
Every state legislature (except Nebraska's) is bicameral. This means that they have an upper house and a lower house. They are similar to the United States Congress in what they look like.
What they do.
State legislatures do similar things as the U.S. Congress does, only for each state.
State legislatures have the power to ratify an amendment of the United States Constitution. 
History.
The first American legislature was created in 1619 by the Virginia House of Burgesses.