Final answer:
Slavery played a critical role in shaping Texas's boundaries. The desire for expansion by slaveholding settlers led to the Texas Revolution and its eventual incorporation into the United States as a slave state, affecting the demarcation of its borders within the context of American expansionism.
Step-by-step explanation:
The role that slavery played in shaping Texas's boundaries is deeply embedded in the state's history of colonization and conflict. Initially, Mexican laws that aimed to limit slavery within its territories were circumvented by American settlers through contractual arrangements that masked the true nature of slavery. As settlers swarmed the Texas territory, the incentive of vast lands, including bonuses for each enslaved person brought along, proved to be a driving force behind the expansion.
The relationship between the expansion of slaveholding settlers into Texas and the tension with the Mexican government that eventually led to the Texas Revolution was a key factor in defining Texas's boundaries. Following independence from Mexico, Texas became a republic where slavery was legal, significantly influencing the United States' decision-making regarding annexation and later statehood, as the balance between slave and free states was a contentious issue at the time.
Eventually, Texas's admission to the Union in 1845, as a slave state, served as a precedent for the eventual demarcation of its boundaries. These delineations were further shaped after the Mexican-American War and the subsequent acquisitions of land, emphasizing the integral connection between slavery, Texas's borders, and the broader ambitions of American expansionism under the banner of Manifest Destiny.