Elections were held in 22 of the state senate's 50 districts.

A statewide map of the 50 state Senate districts in the 1889 elections is provided by the Iowa General Assembly here.

[1] Following the previous election, Republicans had control of the Iowa Senate with 32 seats to Democrats' 16 seats and two Independents.

To claim control of the chamber from Republicans, the Democrats needed to net 10 Senate seats.

Republicans maintained control of the Iowa State Senate following the 1889 general election with the balance of power shifting to Republicans holding 28 seats, Democrats having 20 seats, one Independent, and one member of the Union Labor Party (a net gain of 4 seats for Democrats and 1 seat for the Union Labor Party).