The Confederate states of Arkansas, Texas, and Missouri, the parishes of Louisiana west of the Mississippi, the Indian Territory, and the New Mexico Territory constituted what Richmond editor Edward Alfred Pollard called “the distant and obscure theatre of the Trans-Mississippi.” But “distant and obscure” as it might have seemed to a citizen of Richmond in 1862, the trans-Mississippi was an area of tremendous potential significance. For one thing, at 600,000 square miles, the trans-Mississippi Confederacy comprised more than one-half of the entire Confederate landmass, and the area was as variable as it was vast. In addition, manpower reserves were substantial. In 1860, Arkansas had a white population of more than 324,000; Louisiana, 375,000; Texas, 420,000; and Missouri, in excess of 1,000,000. The black populations of these states were also significant, with Louisiana’s slave population nearly equaling that of its free citizens. Texas had a slave population of more than 180,000, and Arkansas and Missouri each had more than 100,000 enslaved black people. With the coming of emancipation and the enlistment of former slaves into the Union army, many of these men flocked to the colors and played significant roles in the campaigns of 1863 and 1864. Of Louisiana’s black men of military age, 24,052, or 31 percent, joined the army, and in Arkansas, that number was 5,526, or 24 percent. From Texas, however, a state that largely avoided Federal invasion and occupation and therefore held its slaves until the war was ended, only 47 black men enlisted, a mere .001 percent of its prewar slave population....