In the third district, Democratic Senator Cyrus Bussey resigned on January 18, 1862, causing a vacancy in his seat.

[13] In the sixth district, Republican Senator James Conrad Hagans died on September 7, 1863, causing a vacancy in his seat.

In the forty-first district, Republican Senator John Scott resigned on January 18, 1862, causing a vacancy in his seat.

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

[b] Source:[22] District boundaries were redrawn before the 1863 general election for the Iowa Senate: