Surviving are four children: Marlise, Rachel, Daniel, and Joanna Horst, and one grandson, David.
Horst taught Mennonite history and English literature at Eastern Mennonite College from 1955 to 1966 and, while there, was a major influence in developing the collection and policies of the college's Menno Simons Historical Library.
From 1967 to 1985 Horst was the professor of Mennonite history at the University of Amsterdam, filling a newly-created chair.
In 1987 Horst was named scholar-in-residence at the Menno Simons Historical Library; subsequently, the special collections room was named for him.
One of Horst's major contributions to Anabaptist scholarship was, and remains, his 1962 Bibliography of Menno Simons, ca.
