Using the Thor name brand, the Aurora Automatic Machine Company built engines (to the design of Oscar Hedstrom) for the first Indian machines, Reading-Standard, Racycle, Emblem and others. 1901 marks the year that things really started rolling for the Aurora Machine and Tool Company when they were sent a prototype Indian motorcycle for parts study. This ultimately led to the deal that Aurora would make motors and then sell them to Indian. By 1902 137 Indian motorcycles had been produced, all of which were built with Aurora motors in them. With an engine ready at hand, Aurora decided to go the next step and build its own motorcycle, the Thor. By 1903 Aurora created the Thor Motorcycle and Bicycle Company.
It was never stated in the agreement contract that Aurora was bound just to Indian; in fact, it was clearly stated that Aurora could sell to any company it wished as long as a royalty would be returned. With the creation of the Thor, though, the deal between Indian and Aurora ended. The first bikes were created through Aurora "composed of Thor parts" and it has been found that this wasn't just the case with Thor motorcycles. Many other companies had bought from Aurora and they were making almost identical machines with the Thor parts.
In 1903 the first Thor motorcycles were offered to the public. Within just a few years it was considered one of the top American Marques alongside Indian, Harley Davidson, Excelsior, Merkel and Reading-Standard.
The workmanship of the Thor left nothing to be desired, with chain drive to the rear wheel as well as an optional 2-speed rear wheel hub. But, by the dawn of the 1920s Thor, like many of the hundreds of American motorcycle manufacturers, ceased production in the post-WWI years.