Historian Carter G. Woodson declared the second week of February as “Negro History Week” in 1926. He chose that week because it coincided with the birthdays of Abraham Lincoln on the 12th and Frederick Douglass on the 14th.
Black History Month became official in 1976 when white people recognized it. President Gerald Ford announced it was time to “seize the opportunity to honor the too-often neglected accomplishments of black Americans in every area of endeavor throughout our history.” Subsequently, each year the President has proclaimed February as Black History Month.
Notably, in his 2017 declaration the current occupant of the White House, a renowned historian in his own right, stated, “Frederick Douglass is an example of somebody who’s done an amazing job and is being recognized more and more, I notice.”
From the 2019 declaration:
This year’s theme, “Black Migrations,” highlights the challenges and successes of African Americans as they moved from farms in the agricultural South to centers of industry in the North, Midwest, and West—especially the migrations that occurred in the twentieth century. Through these migrations, millions of African Americans reshaped the demographic landscape of America, starting new lives in cities such as Philadelphia, Detroit, Chicago, and New York City.
Read the entire proclamation here (not likely that it was written by the current President).