In 1958, the Town of Whitby purchased property from Samuel Trees at the corner of Dundas and Henry Streets to construct a new, larger municipal building. This new building replaced the aging Town Hall located at Brock and Colborne Streets which was built in 1877. The Municipal Building at 405 Dundas Street West was officially opened in 1960 and served as Whitby’s administrative centre until 1977 when offices were moved to the building located at 575 Rossland Road East.

Like the Town of Whitby, the Carnegie Library continued to grow during this time. In addition to books, the collection now included gramophone records and the children's department took over the entire basement of the Carnegie building. In order to accommodate this growth, the Library moved some of its collections into the basement of the Municipal Building in 1974.