It may be pertinent right here to say that when the United States buys or comes into possession of a tract of land it becomes the property of the country and is called a Territory, and under the Constitution it is so treated, without representation in Congress until such time as it is admitted into the Union and becomes one of the United States.
This great Territory comprising 370,472 square miles originally belonged to Mexico. In 1820 Moses Austin, a native of Connecticut, obtained a grant of land and threw it open to settlement by people from the United States, mostly the Southern States. In a few years more than 20,000 had settled there and the strong Anglo-Saxon spirit of liberty began to rebel against the oppressive Mexican rule. In a few years this feeling burst into an open revolt. Texans met and declared their independence and formed a Republic and placed an army in the field under Gen. Sam. Houston. He met the Mexicans under Gen. Santa Anna at San Jacinto in 1836 and gained a complete victory, thus achieving the independence of Texas. Next year Texas applied for admission into the Union but no action was taken by Congress for several years. Meantime in the north a strong sentiment had developed against the institution of slavery. The subject was vigorously agitated in the pulpit, in literature and in public. The Southern people, perceiving the strength of the opposition to their favorite institution, determined in self defense to acquire more territory for the sake of the strength additional votes would give them, and so in 1844 the proposal to admit Texas came up in Congress in earnest.
No concealment of the underlying purpose was made by the Southern Congressmen who led the movement. A bitter struggle followed but the annexationists prevailed and in 1845 the “Lone Star State,” as Texas had been called, was added to the Union. The South welcomed the new comer with great demonstrations, but the greetings of the North were not cordial, for in that section it was clearly understood that a great extension was given to slave territory.
The vast territory included in these two Territories was acquired mostly from Mexico in 1848 as one of the terms of the treaty of peace between the United States and that country made after the war of 1846-47. The war with Mexico was brought about by the refusal of the Mexican Government to concede the claims of Texas to land between the Rio Grande and the Nueces Rivers. The actual rights in the case were somewhat obscure, but war was eagerly undertaken by the Southern people, who believed that a further extension of slave territory would be the ultimate result. The North was less enthusiastic, for this reason, but sent a quota of troops into the field before whose valor, directed by commanding officers who later became prominent in the great war of the Rebellion, the Mexican armies were defeated. The United States paid Mexico $15,000,000 for the territory ceded under the treaty and in addition paid $3,500,000 in settlement of the claims of private individuals. The boundary line remained in dispute for five years more, until 1853, when James Gadsden negotiated a treaty with Mexico settling all questions. Under its terms the United States gained the Mesilla Valley, forming the southern part of what is now New Mexico and Arizona, and comprising 20,000,000 acres. The United States paid Mexico $10,000,000 for this land which was afterwards known as the Gadsden purchase and is so marked on the larger maps issued by the Interior Department at Washington. Including the territory acquired by the Mexican war, the State of Texas and that included in the Gadsden purchase, the whole area is sufficient to make one hundred and seventy States the size of Connecticut.