they decided it because that area was the most vacant to border hoppers or immigrants who could pose as a threat
The Emancipation Proclamation granted freedom to the slaves in the Confederate States if the States did not return to the Union by January 1, 1863. In addition, under this proclamation, freedom would only come to the slaves if the Union won the war. By the President of the United States of America: A Proclamation. Despite promises of equal treatment, blacks were relegated to separate regiments commanded by white officers. Black soldiers received less pay than white soldiers, inferior benefits, and poorer food and equipment.
There are two reasons one was to follow after Pancho Villa and 2nd was to start a revolt (someone already asked this question XD)
