Remembered for his roles as Nels Oleson and Doc in, respectively, NBC's Little House on the Prairie and ABC's Voyage to the Bottom of the Sea, this 20th-century American television actor also appeared in episodes of Barnaby Jones, Mannix, and Bonanza.
He began his career as a professional stage actor, appearing in several productions at Chicago's Goodman Theatre.
His film credits include roles in the 1973 Clint Eastwood movie High Plains Drifter and in the 1971 Robert Wise-directed feature The Andromeda Strain.
Born in Zion, Illinois, he later lived in Chicago and Los Angeles. His marriage to Barbara Collentine lasted from 1948 until his death in 2014.
He and Michael Landon appeared together in Little House on the Prairie, as well as in two episodes of Highway to Heaven.