In 1696, one of the earliest books on swimming, The Art of Swimming by Thevenot was written.  The 1st modern swimming competitions began in 1837.  Coaches and swimmers have been searching for ways to improve stroke efficiency since competitive swimming began. 

Butterfly was developed from research on how to make breaststroke faster. David Armbruster developed a double over arm recovery that combined the breaststroke whip kick. Jack Sieg mimicked a dolphin's kick and it turned into the flutter kick we use today. Sieg and Armbruster combined  their techniques. Swimmers could swim 100 yards in one minute. Under the breaststroke rules, the flutter kick was illegal.  Butterfly became a separate stroke in 1956.

Backstroke made its first appearance at the 1900 Olympic Games. It is the only competition that starts with a push off of the wall.  In 1935 through 1945, Adolph Kiefer dominated the backstroke field using a straight arm recovery.  However, the Australians found that by slightly bending the arm they could get more thrust.  Swimmers went faster by doing a streamlined dolphin kick underwater.  In 1989, a rule was set that said you can only dolphin kick for 15 meters.

Breaststroke used to be swum with one's head totally out of the water.  Breaststroke is the oldest of the four strokes.  It is, however, the least efficient.  It is called the "silent stroke" because swimmers could make better time underwater than on top. Some swimmers used to stay underwater the whole time while swimming.  A few swimmers even passed out!!  The rules then changed and your head was able to be out of the water. 

Freestyle began when, two Native Americans, Flying Bull and Tobacco, entered a British competition in 1844.  They took 1st and 2nd using a front crawl stroke.  They were much faster than the British.  Arthur Trudgen concluded that the Indians had  more speed with an overhand stroke.  He taught others the new stroke technique. Swimmers shaved 10 seconds off  the fastest 100 yard time.  Frederick Cavill developed the stroke we use today.  He also realized that the kick was different.  So, Cavill taught his sons the new kick.  His sons splashed records.  The new stroke became known as the crawl.