In 1977 Pope Paul VI awarded Longenecker the Benemerenti Medal to honor his extensive public service. Longenecker also served as national president of Sigma Xi Scientific Research Society in 1980. In 2006 he established a Trustee Matching Scholarship for Penn State. Longenecker moved to Birmingham, Alabama where his wife died in 2005. He would later marry his second wife, Katherine Butler Longenecker. He was living in Birmingham at the time of his death where he was a member of the Cathedral Church of the Advent. His papers are held by the Penn State University library.