In 1845 Texans voted overwhelmingly to join the Union. They voted just as overwhelmingly to secede in 1861. The story of why and how that happened is filled with colorful characters, such as the aged Sam Houston, and with the southwestern flavor of raiding Comanches, German opponents of slavery, and a border with Mexico.

Texas was unique among the seceding states because of its ambivalence toward secession. Yet for all its uniqueness the story of the secession of Texas has broad implications for the secession movement in general. Despite the local color and the southwestern nature of...