Give me a summary of the history of Thackeray Hall at the University of Pittsburgh based on this passage.
Thackeray Hall used to be the building for the National Union Fire Insurance Company until it was purchased by the University of Pittsburgh in 1968 for $1.875 million. First, it was used for faculty offices, then later known as the Social Sciences Building until it was renamed Mervis Hall. In 1983, it was renamed Thackeray Hall and has housed the university's Department of Mathematics since then.