The Hercules was a steam driven tugboat built in 1907 for ocean towing. The Hercules towed logs and barges up and down the US Pacific coast, and supplies to build the Panama canal. In 1924, the Hercules was converted into a railroad tug to ferry car floats across San Francisco Bay.
In the 70's, she was retired and refurbished as a national landmark. She currently resides at the San Francisco Maritime Museum. Hercules from the TV series is based off of this tug.