Hassel was originally known as Saint Louis. Sometime during 1895 the St. Louis name was dropped in respect to a pioneer miner, Joseph E. Hassel and the request of the post office. Other names for Hassel at various times were Knoxville, Placerville and Florence City.

As early as 1866 placer gold was discovered on Indian Creek, near Hassel. During its active mining years the creek grossed about $5,000,000 in gold. Placer mining ended about 1880 however stamp mills and some hydra sluicing operations continued reviving the camp.

Hassel was famous for its huge Diamond Hill Stamp Mill of one hundred twenty stamps which operated at full capacity from 1898 to 1900. The mine is still in operation and known as the Apollo Mining Co. Mine. Some old buildings still remain.