Hartley, District 1, was elected to office in 2008 and assumed his post on Jan. 1, 2009. He served on varied committees before being elected chairman in January 2012.
Reynolds represents District 3 and Clark, District 2. They were both elected in 2008 and assumed duties in January 2009.
They were given a round of applause after a framed copy of a resolution was read and presented by Manager Matt Denton.
Each expressed thanks for support of other board members and the people of Polk.
"It has been my pleasure to serve each of you," Hartley said.