In 1775 what was the largest city and what was its population

Boston, New York ... Charles Town [Charleston]—and none had more than 40,000 people in 1775.

At the time of the nation’s independence the total population in the U.S. was 2.5 million. Philadelphia was the largest city with 40,000 residents – which would only fill about half the capacity at Lincoln Financial Field where its football team plays home games today. The Quaker-populated city back then was very peaceful and civil, very unlike the Eagle fans of today.