State Sen. Kirk Dillard has officially resigned from the Illinois Legislature to become chairman of the Regional Transportation Authority.

Illinois Senate Republicans said in a Monday news release that Dillard stepped down from his 24th District seat. The Hinsdale Republican was named to the RTA position in June after more than 20 years in the Illinois Legislature.

Dillard made two unsuccessful Republican primary bids for governor.

The RTA provides financial oversight for the Chicago Transit Authority, Metra and Pace.

The Chicago Sun-Times reports that Dillard submitted his resignation in a July 31 letter to the secretary of the Illinois Senate. The resignation was effective 11:59 p.m. on Sunday.