The first tow truck wasn’t built on a heavy-duty truck chassis as expected, but rather on a 1913 Cadillac. As recounted by the Chronicle and other sources, in 1916, Ernest Holmes, a mechanic from Chattanooga, Tennessee, received a call from his former business school professor, John Wiley. Wiley had driven his Ford Model T off the road and ended up in a creek. It took Holmes eight hours, six men, and considerable effort to get the car out. This experience inspired Holmes to modify a three-year-old Cadillac, which had a sturdy 120-inch wheelbase and a 365.8-cu.in. L-head four-cylinder engine. He equipped it with a crane and pulley system designed to lift and secure vehicles for towing.

After adding outriggers for stability, Holmes filed for a patent for his invention (US Patent (617) 533-3775 in November 1917. With the patent secured, he shifted his business focus to manufacturing Holmes Wrecker tow trucks, creating the first "towing service" and promoting them as tools to help mechanics attract more business. He went on to invent numerous improvements to tow trucks and developed various vehicle lifts, creepers, and jacks until his passing in 1945.

This information is sourced from Wikipedia.