The Dvorak Simplified Layout was one of several attempts throughout the history of the keyboard at improving on its original QWERTY layout. The Dvorak Simplified layout was patented in 1936 (patent no.2,040,248) but its developers were working on it as early as 1932, which is when the patent was applied for. The two men who are credited, and whose names appear on the patent paperwork, are Dr. August Dvorak (1894 - 1975), who was a professor of education at University of Washington at the time, and his brother-in-law, Dr. William Learned Dealey (1892 - 1986), who was also a professor of education but at North Texas State Teacher's College.
In the early 1930s, Dvorak and Dealey, as reported by the Arizona Republic on January 24, 1985, were prompted to address the traditional keyboard layout by a professor of statistics at Brown University. The two men took on the project and applied for a grant to fund it from the Carnegie Foundation. The Dvorak layout was just the latest attempt to streamline the keyboard. The original layout, QWERTY, was developed specifically for the Sholes & Glidden typewriter of 1873 which typed only in uppercase and had a circular, upstrike typebar arrangement. Its layout was optimized to these attributes. One would assume that as the typewriter progressed, so too should have the keyboard, but it did not.
That's not to say that there weren't a multitude of attempts to revise the layout. One of these was Hammond's "Ideal" layout of 1884, while another was Blickensderfer's "Scientific" one of 1893. There were also typewriters with double (full) keyboards, typewriters with no keyboards (index typewriters) and everything in between. The index typewriters proved too slow, and because the S&G had no market competition for about 10 years, and because humans are creatures of habit, QWERTY became the "universal" layout. Hammonds and Blicks eventually succumbed to market pressures and offered the universal layout, too.
The Dvorak layout placed 10 of the 13 most commonly used letters, the ones that comprise 70% of the English lexicon, on the middle, home row. QWERTY achieves just 32%. The Dvorak layout also increased the typist's accuracy and increased speed by an average of 35% (the fastest typist in 1984, Barbara Blackburn, set a new record of 180 words per minute with Dvorak). There was a caveat, however. Most of the words typed with the Dvorak layout are to be executed with the right hand because it was developed for right-handed users whom make up the majority of the population.
Despite the benefits, Dvorak never caught on. There was an increase in interest in the mid 1980s when word processors were introduced, but only about 60,000 units were ordered with the layout. QWERTY was estimated to be on over 20 million keyboards at the time.
It's probably safe to state that each keyboard layout was a good fit for the typewriter it was designed. The Dvorak layout probably wouldn't have made sense on a Hammond or Blick but it's ideal for the archetypal typewriter: one with a four-row keyboard, a single-shift mechanism and a frontstrike typebar arrangement.