Spencerville is an unincorporated community located in Spencer Township, DeKalb County, Indiana. The only covered bridge in DeKalb County is located in Spencerville.The Spencerville post office was established in 1839. Spencerville was named for John Spencer, relative of one of the founders.Spencerville is located at 41°16′59″N 84°55′19″W / 41.28306°N 84.92194°W / 41.28306; -84.92194.