When the Reconstruction constitutional convention reconvened on Dec. 4, 1868, Radical Republicans sharpened their knives in eager anticipation of carving up Texas like a Christmas turkey.

Any Texan, who passed the required courses in junior high, knows that as a condition of admission to the Union the Lone Star State retained the right to subdivide into as many as four separate parts. Less well known is how often the idea of two, three, many Texas’ was tossed around and how close the state...