was anyone the president before him?
No, he was the first president of the United States
Presidency of George Washington
The presidency of George Washington began on April 30, 1789, when Washington was inaugurated as the first president of the United States, and ended on March 4, 1797. Washington took office after the 1788–89 presidential election, the nation's first quadrennial presidential election, in which he was elected unanimously. Washington was re-elected unanimously in the 1792 presidential election, and chose to retire after two terms. He was succeeded by his vice president, John Adams of the Federalist Party.

states that entered the union during presidential terms North Carolina, Rhode Island, Vermont, Kentucky, Tennessee when was george elected as president? April 30, 1789
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Presidency of George Washington [SEP] Introduction
Congress passed the Tariff of 1789, the Tariff of 1790, and an excise tax on whiskey to fund the government and, in the case of the tariffs, address the trade imbalance with Britain. Washington personally led federal soldiers in suppressing the Whiskey Rebellion, which arose in opposition to the administration's taxation policies. He directed the Northwest Indian War, which saw the United States establish control over Native American tribes in the Northwest Territory. In foreign affairs, he assured domestic tranquility and maintained peace with the European powers despite the raging French Revolutionary Wars by issuing the 1793 Proclamation of Neutrality.