Sagaciously anticipating this contingency, the Southern States had been largely instrumental in setting up the independent State of Texas, and were now urgent in their demand for her annexation to the Union. Two days before the signing of the Iowa and Florida bill, Congress passed, and President Tyler signed, a joint resolution, authorizing the acquisition, annexation, and admission of Texas. But even this was not all. The joint resolution contained a guarantee that "new States, of convenient size, not exceeding four in number, in addition to the said State of Texas," and to be formed out of her territory, should hereafter be entitled to admission--the Missouri Compromise line to govern the slavery question in them. The State of Texas was, by a later resolution, formally admitted to the Union, December 29, 1845. At this date, therefore, the slave States gained an actual majority of one, there being fourteen free States and fifteen slave States, with at least equal territorial prospects through future annexation. If the North was alarmed at being thus placed in a minority, there was ample reason for still further disquietude. The annexation of Texas had provoked the Mexican war, and President Polk, in anticipation of further important acquisition of territory to the South and West, asked of Congress an appropriation of two millions to be used in negotiations to that end. An attempt to impose a condition to these negotiations that slavery should never exist in any territory to be thus acquired was the famous Wilmot Proviso. This particular measure failed, but the war ended, and New Mexico and California were added to the Union as unorganized Territories. Meanwhile the admission of Wisconsin in 1848 had once more restored the equilibrium between the free and the slave States, there being now fifteen of each.