"The inspiration was an accident. While operating his lithographic press he [Rubel] noticed that if he failed to insert paper the stone plate would transfer its image onto the rubber impression cylinder. When he then placed paper into the machine it would have the image on two sides, one from the stone plate and one from the rubber impression cylinder. To Rubel’s amazement, the image from the rubber impression cylinder was much clearer; the soft rubber was able to give a sharper look than the hard stone litho plate. Soon he created a machine that repeated this original “error”. This process was also noted by two brothers, Charles and Albert Harris, at about the same time. They produced an offset press for the Harris Automatic Press Company not long after Rubel created his press" (Wikipedia article on Offset printing, accessed 04-22-2009).
Rubel's first offset press was operated in Rubel's New York plant for a year before it was sold to the Union Lithographic Company of San Francisco for $5,000. After it had been shipped out to California, the press waited out the 1906 San Francisco earthquake and fire on a wharf in nearby Oakland. It began operation in San Francisco in 1907. Rubel's original offset press is preserved in the Smithsonian Institution, Washington, D. C.