On the annexation of Texas, popular sentiment, even in his own party, was far from unanimous, but the party was, nevertheless, thoroughly committed to it. After the election, when it appeared that Tyler was quite as favorable to the measure as his incoming Democratic successor, Douglas was one of those who came forward with a new plan for annexing territory by joint resolution of Congress, and in January, 1845, he stated as well as it ever has been stated the argument that Texas became ours by the Louisiana Purchase of 1803, and was without the consent of her people retroceded to Spain by the treaty of 1819. When President Polk sent in his announcement that war existed by the act of Mexico, Douglas was ready with a defense of that doubtful _casus belli_ and an ardent support of the army bill which followed. His speech on the army bill was an admirable exhibition of his powers, and it was the best speech on that side in the debate. Adams, who interrupted him, was instantly put upon the defensive by a citation from the argument which he himself, as Secretary of State, had made in 1819 for the American claim to the line of the Rio del Norte. When he asked if the treaty of peace and boundaries concluded by Mexico and Texas in 1836 had not since been discarded by the Mexican government, Douglas retorted that he was unaware of any treaty ever made by a Mexican government which was not either violated or repudiated. Adams came finally to acknowledge the unusual powers of the Western "_homunculus_" as a debater. But the reputation and the influence won in the House of Representatives were to be extended in a more favorable arena. In 1846, Douglas being now thirty-three years of age, the Illinois legislature elected him United States senator for the six years beginning March 4, 1847. In April, 1847, he was married to Martha, daughter of Colonel Robert Martin, of Rockingham, N.C., a wealthy planter and a large slaveholder. Active as he continued to be in politics, he found time for business as well as love-making. He invested boldly in the lands over which Chicago was now spreading in its rapid growth and made the young city his home. His investments were fortunate, and within a few years he was a wealthy man according to the standard of those times. He used his wealth freely in hospitality, in charity, and in the furtherance of his political enterprises. In the year 1856, the corner-stone of the University of Chicago was laid on land which he had given.