America’s 99 state legislative chambers have varying term lengths and likewise conduct their elections on different schedules. The map above (which you can also find in larger size here) will help you make sense of when each state’s legislative seats are up each decade. Every state is sized the same, with each state’s upper chamber making up the top half of each hexagon and the lower chamber on the bottom (Nebraska’s unique unicameral legislature takes up a whole hexagon).
As illustrated, most states have elections every two years that coincide with even-year federal elections, although many upper chambers (as well as the lower chamber in North Dakota) have four-year terms where only some seats are up every two years. These are known as “staggered” terms, in much the same way that only a third of seats in the U.S. Senate are up each cycle.
In most staggered legislative chambers, half of all seats are up each election, though some states use a hybrid system known as “2-4-4,” where legislators serve one two-year term and two four-year terms every 10 years. These chambers are marked with asterisks on the map above.
A minority of states hold elections only in odd-numbered years, or exclusively in either midterms or presidential election years, while the Minnesota and New Jersey Senates follow unusual schedules all of their own.
The map below shows which party controls each legislative chamber following the 2018 elections. Republicans hold 62 chambers compared to 37 for Democrats; prior to the midterms, the split was 67-32 in favor of the GOP. Today, Minnesota is the only state in the country to feature divided control of its legislative chambers, marking the lowest number of such states in 104 years.