[1] This was the first legislative session after the redistricting of the Senate and Assembly according to a decision of the Wisconsin Supreme Court in 1964.

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

Senators representing odd-numbered districts were serving the third and fourth year of a four-year term, having been elected in the general election of November 6, 1962.

[1] The governor of Wisconsin during this entire term was Republican Warren P. Knowles, of St. Croix County, serving a two-year term, having won election in the 1964 Wisconsin gubernatorial election.

Reynolds v. Zimmerman, decided by the Wisconsin Supreme Court in May 1964.