states that entered the union during presidential terms
North Carolina, Rhode Island, Vermont, Kentucky, Tennessee
Presidency of George Washington
When the federal government began operations under the new form of government in the spring of 1789, two states—North Carolina and Rhode Island—were not yet members of the Union as neither had ratified the Constitution. Both did so while Washington was in office, thereby joining the Union: North Carolina, November 21, 1789; and Rhode Island, May 29, 1790. While North Carolina joined of its own accord, Rhode Island only joined the Union after the federal government threatened to break off trade relations.

Three new states were admitted to the Union (each on an equal footing with the existing states) while Washington was in office: Vermont, on March 4, 1791; Kentucky, on June 1, 1792; and Tennessee, on June 1, 1796.
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Presidency of George Washington [SEP] States joining the Union
When the federal government began operations under the new form of government in the spring of 1789, two states—North Carolina and Rhode Island—were not yet members of the Union as neither had ratified the Constitution. Both did so while Washington was in office, thereby joining the Union: North Carolina, November 21, 1789; and Rhode Island, May 29, 1790. While North Carolina joined of its own accord, Rhode Island only joined the Union after the federal government threatened to break off trade relations. Three new states were admitted to the Union (each on an equal footing with the existing states) while Washington was in office: Vermont, on March 4, 1791; Kentucky, on June 1, 1792; and Tennessee, on June 1, 1796.