Euclid of Alexandria: 325 B.C. ~ 265 B.C. (?) The dates are not exact as little is known about Euclid's life. It is generally believed that he studied under the students of Plato and it is known that he established a school of mathematics and taught at the library in Alexandria. His most well-known work is The Elements, which is a wonderfully organized development of the plane and solid geometry, geometric algebra, theory of proportions, number theory, and the theory of irrational numbers known then. The work is divided into 13 books and contains 465 propositions. Beginning in Book I with 5 postulates, 5 common notions, and 23 definitions, Euclid develops the basic properties of plane geometry from the construction of an equilateral triangle in Proposition 1 to his beautiful...

In the book one can see the strong commitment to a logical development of ideas that Euclid used throughout the work. This "first mathematics text" set a standard for mathematics following it to this day, making him one of the largest influences of all.
Even though little personal information exists about Euclid, two stories about him have survived. It is known that Ptolemy was a student in Euclid's school for quite some time and he is reported to have asked if there was an easier way to master geometry; to this Euclid responded that although the king could travel on royal roads, "there is no royal road to geometry."; a…