The Twentieth Wisconsin Legislature convened from January 9, 1867, to April 11, 1867, in regular session.

Senators representing odd-numbered districts were newly elected for this session and were serving the first year of a two-year term.

Assembly members were elected to a one-year term.

Senators representing even-numbered districts were serving the second year of their two-year term, having been elected in the general election held on November 7, 1865.

[1] The governor of Wisconsin during this entire term was Republican Lucius Fairchild, of Dane County, serving the second year of a two-year term, having won election in the 1865 Wisconsin gubernatorial election.