The legislative article vests the legislative power, other than the initiative and referendum processes, in a bicameral body. The number of senators may not be less than twenty-five nor more than thirty-five; the house of representatives must have between fifty and seventy-five members. Since 1970, the Senate has had thirty-five members and the house seventy members The state is divided into thirty-five legislative districts, each electing two representatives and one senator.
Sessions are held annually. In odd-numbered years, the legislature meets for forty days and in even-numbered years for thirty-five. All sessions commence on the second Tuesday in January.
The Governor is empowered to call special sessions of the legislature for specific purposes. There have been eighteen such sessions since statehood. A 1990 constitutional amendment allows for a special session when two-thirds of the members of each house petition for a special session for a specific purpose.
Legislators must be qualified voters in their legislative districts, at least twenty-one years old, citizens, and residents of the state for two years immediately preceding election Terms are for two years. A 1992 constitutional amendment limits members to four consecutive terms in each chamber.
In 1951, the South Dakota Legislature established the Legislative Research Council to provide full-time staff support to the legislature.
In 1898, South Dakota became the first state to authorize the initiative and referendum procedures for ordinary legislation. The initiative process was extended to include constitutional amendments in 1972. Prior to that time all constitutional amendments originated with the legislature and were submitted to popular vote. Initiated measures permit the voters to add to, amend or repeal existing laws; the referred law process allows the voters to approve or reject measures passed by the legislature. However, the referendum does not apply to laws which are "necessary to the immediate preservation of the public peace, health or safety" or which are necessary for the support of state government and its existing institutions.
Petitions to initiate or refer legislation require signatures equal to five percent of the votes cast for Governor in the last general election. Petitions to initiate a constitutional amendment require signatures equal to ten percent of the votes for Governor in the last general election.