In 1970 the building's historic restoration began, directed by a committee led by Professor Margaret N. Keyes. Prof. Keyes, did much scholarly detective work to ensure that the building was returned to its original Greek Revivalist elegance. Keyes and the committee also hoped to capture the essence of Old Capitol's three distinct historical periods: the territorial government period, the state government period, and the University's long and continuing use.

Old Capitol reopened to the public on July 3,1976, as a National Historic Landmark. Continuing restorative work on Old Capitol is made possible through public funds and private gifts, as well as the donation of period furnishings and historic documents.

The six-year restoration project begun in 1970 accomplished its goals: to restore the building to reflect its total history and to serve as a "living museum" with some rooms of historical furnishings and exhibits and others providing space for ongoing University functions. Painstaking research has allowed authentic refurnishing of several rooms, some with what might well be original pieces used by state legislators in the 1840s. As Margaret Keyes wrote in her book Old Capitol: Portrait of an Iowa Landmark, "A restoration can probably never be considered finally completed or finished. Historic facts that had been missed may be discovered or additional original furniture and accessories may be found....In the years since the 1976 dedication and grand reopening of Old Capitol, the building has changed measurably and yet it seems unchanged in spirit."