Colt's methods were at the forefront of the Industrial Revolution, and his successes secured Hartford's place as a major 19th century manufacturing center. It is estimated that his company produced over 400,000 revolvers in its first 25 years of manufacturing. His use of interchangeable parts helped him become one of the first to exploit the assembly line. Moreover, his innovative use of art, celebrity endorsements, and corporate gifts to promote his wares made him a pioneer in the fields of advertising, product placement, and mass marketing. His business practices were also innovative, involving a shrewd use of patents to protect his products, as well as new developments in marketing and business organization to create a highly successful business which long outlived him.