The Pumpkin Heads by A.K. Roche (Prentice-Hall, 1968).
I found this while searching online for books that take place in my state of Connecticut. This story takes place in my city of New Haven so I had to check it out. It's presented as a story explaining why people in New Haven are calling "pumpkin heads" (which is not a real thing), but there is a note in the back that explains the truth. The author was inspired by reading an anecdote in a General History of Connecticut by Revered Samuel Peters, a Loyalist during the Revolutionary War who made up stories exaggerating the conditions in Connecticut to get back at the people who drove him out and back to England. This makes a lot of sense, as the story definitely makes the people of New Haven seem pretty foolish!
In the story, men of New Haven would line up to get their haircut which was cut while wearing a special cap so that they all had the same length hair. When the cap is lost, they try using various bowls and baskets, but nothing is the right size. That is, until a wise old woman suggests a pumpkin cut in half.