Carter G. Woodson, by many considered the father of African-American Studies and the founder of the Association for the Study of African-American Life and History, created the first celebration of black history in 1926.
It was originally called Negro History Week and held during the second week of February to honor Abraham Lincoln, who was born 12 February, and Frederick Douglass, who was born 14 February. Since there were already celebrations around Lincoln's and Douglass' dates of birth, Woodson reasoned that people would not be opposed to celebrating the achievements of African-Americans during that entire week, also.
50 years later, in 1976, Negro History Week was lengthened to include the entire month of February, thus we now celebrate Black History Month.
Omega Psi Phi Fraternity, Inc., of which Dr. Woodson was/is a member, is also tied to the creation of Black History Month?
To read more about the beginnings of Black History Month, Carter G. Woodson and his organizations and publications, an excellent place to start is the Association for the Study of African-American Life and History (ASALH).
Each year, ASALH is responsible for setting a new theme for Black History Month.
Visit their site to see this year's theme.