This is the emblem used by the 1st division of the Fifth Corps of the Army of the Potomac during the American Civil War.
If you have ever watched the film Gettysburg, you may have noticed a symbol on the top of some of the caps belonging to the men under Colonel Chamberlain's command. This is that symbol. Colonel Chamberlain's 20th Maine regiment was part of the 1st division of V Corps.
The V Corps had three divisions. The color of the emblem was used to represent a specific division of the corps; red meant 1st Division, white meant second division, and blue meant third division.