The U.S. Navy’s involvement with the submarine dates from 1888 when the Bureau of Construction and Repair (BUC&R) sponsored a design competition that brought John Holland a naval contract to build the experimental Plunger. As the new century dawned, prominent American naval leaders like Admiral George Dewey called the submarine a real threat to international surface forces, leading the Navy to acquire its first submarine in 1900. Overcoming competition from fellow American inventor, Simon Lake, Holland sold his newest model, Holland VI, to the Navy for $150,000, April 11, 1900. This 64-ton submarine, commissioned as USS Holland, or SS 1, Oct. 12, 1900, was equipped with an Otto-type gasoline engine for surface running and electric motors for submerged operations.
For the next week, submarines will be the key story at theleansubmariner.com
Mister Mac
theleansubmariner 
This is cool. How long has this commemorative day been recognized?
Not sure. I know we have recognized April as submarine month because of the original submarine purchase but am not sure about the day being recognized in this way.
1. Looks like the Navy used a 594 class on the illustration.
2. The day before, April 10, will be the 50th anniversary of the loss of the Thresher.