Senn was born inMadison, Wisconsin,[2] to Swiss philologist and lexicographer,Alfred Senn [ru]. His father taught at theUniversity of Lithuania, where he met his future wife. After they married, they moved to the United States in 1930 or 1931, along with two daughters.[3]
Senn received a BA in 1953 from theUniversity of Pennsylvania and then an MA in 1955 and a PhD in 1958 fromColumbia University in East European history.[2][4] He started teaching at the University of Wisconsin–Madison in 1961, and he retired as professor emeritus.
Senn was the author of various books and numerous scholarly articles. Many of his works center on thehistory of Lithuania. His bookGorbachev's Failure in Lithuania was awarded the Edgar Anderson Presidential Prize by theAmerican Association of Baltic Studies in 1996. He died at his home in Madison on March 8, 2016.[5]