Start of the National Negro Baseball League

The Afro-American - February 27, 1920

Gary Ashwill, over at agate type, featured a few articles about the Negro National League's birthday.  I found another article that lists the players for each of the six teams.

UPDATE: I found a few more supporting articles.

The Tulsa Star - February 14, 1920

The Tulsa Star - February 28, 1920

Tom Wilson, Elite Boss, Drops Dead

Afro American - May 17, 1947

New Pitching Star at Fort Huachuca

The Afro American - September 4, 1943

Walter McCoy later went on to play for the Chicago American Giants and the Kansas City Monarchs.  For more information see Gary Bedingfield's Baseball in Wartime entry on McCoy.

No Baseball Color Line at Grenier Field

The Afro American - June 12, 1943

In the middle of WWII Grenier Field was an Army Air Corps training site. As at many other service bases the game of baseball was played. I'm not sure when teams became integrated for service teams, but in 1943 we can see that there was no color line in New Hampshire.