A wreath, sent from President Barack Obama, was placed at the memorial by a Navy official at 11:30 a.m.; Nixon served on active duty with the Navy during World War II.
Nixon is the only U.S. president born in California and the only one ever to resign from office.
Free admission to the library was offered all day. Hours of operation are from 10 a.m. to 5 p.m.
City News Service contributed to this story.