Final answer:
The largest diamond found in the US was found in Arkansas at the Crater of Diamonds State Park.
Step-by-step explanation:
The largest diamond found in the US was found in Arkansas at the Crater of Diamonds State Park. The park is the only diamond-producing site in the world open to the public. The largest diamond discovered at the park is known as the 'Uncle Sam' diamond, weighing 40.23 carats.