Which President had the most states admitted to the union during his administration?

During the term of Benjamin Harrison (1889-1893), 6 states were admitted to the Union, more than under any other President. The states were North Dakota, South Dakota, Montana, Washington, Idaho, and Wyoming.

The original 13 states were already part of the Union in 1789, so George Washington's two terms (1789-1797) saw only three "new" states, If the Confederate states were considered by "re-admission", Andrew Johnson (1865-1869) would have the most with 8 of the Southern states regaining representation in Congress.