Lee Harris was sworn in as mayor during a ceremony at the Cannon Center. He will resign his position in the state senate.
The Shelby County Commission also has eight new commissioners and is now under Democratic control.
Activist Tami Sawyer is one of the new commissioners and is one of three women on the commission.
Thursday's ceremony included many of the county's incoming elected representatives. Newly elected sheriff Floyd Bonner will be sworn in next week.