Harold Camping isn't the first self-proclaimed prophet to calculate a date for the rapture. In 1833, William Miller predicted the rapture would occur around 1843. The Millerite movement gradually gained followers in the early 1840s, culminating in the Great Disappointment when Jesus failed to appear in October, 1844. Despite their disappointment, the Millerites made some interesting theological charts. Take a moment and check them out.
Of course, 19th century Americans didn't take Millerites all that seriously. They often were lampooned for their beliefs, as evidenced by this 1843 caricature of a Millerite preparing for the rapture. Source.