April 15, 1707 - September 18, 1783
Born and educated in Basel, he was a mathematical child prodigy. He worked as a professor of mathematics in Saint Petersburg, later in Berlin, and then returned to Saint Petersburg. He is the most prolific mathematician of all time, his collected work filling 75 volumes. He dominated eighteenth century mathematics and deduced many consequences of calculus. He was completely blind for the last seventeen years of his life, during which time he produced almost half of his total output.
The Seven Bridges of Königsberg is a problem inspired by an actual place and situation. The city of Königsberg, Prussia (now Kaliningrad, Russia) is set on the river Pregel, and included two large islands which were connected to each other and the mainland by seven bridges. The question is whether it is possible to walk with a route that crosses each bridge exactly once, and return to the starting point. In 1736, Leonhard Euler proved that it was not possible. Eventually this led to Euler's explaination of graph theory.