President John Tyler had a particularly difficult time filling vacancies. Smith Thompson died in office December 18, 1843. His replacement, Samuel Nelson, was in office starting February 14, 1845. That’s a vacancy of 424 days. Henry Baldwin died in office April 21, 1844. His replacement, Robert Cooper, was in office starting August 4, 1846. This vacancy lasted 835 days because Tyler could not get the Senate to work with him. During Tyler’s presidency, the Senate rejected nine separate Supreme Court nominations!
Most recently, Abe Fortas resigned May 14, 1969. His replacement, Harry Blackmun, was in office starting June 9, 1970, making the gap just longer than a year.