According to History.com
Ironically, the man with the shortest White House tenure delivered the longest inaugural address in history, which may have been his undoing. This first presidential speech, delivered on a bitterly cold March morning, clocked in at one hour and 45 minutes. Harrison went to bed at the end of inauguration day with a bad cold that soon developed into a fatal case of pneumonia. Some historians have claimed that a case of hepatitis may also have contributed to his demise.
Inaugural addresses aside, are there (other) speeches by a sitting US president longer than that one (1h 45min)?