Slavery had become one of the leading questions of the day. To keep the balance between the North and the South, states were often admitted in pairs, one free and one slave state. In 1845 there were in the Union thirteen free and fourteen slave states. The decade between 1840 and 1850 witnessed the war with Mexico and the acquisition from her of our vast southwestern territory,--Texas, California, Utah, Nevada, Arizona, New Mexico, and some interior lands to the north of these. The South was chiefly instrumental in bringing about this extension of our boundaries, hoping that this additional territory would be open for the employment of slaves and would tend to make more nearly even the influence of each section in the national government. SUMMARY With the publication of Irving's _Knickerbocker's History of New York_ in 1809, the literary center of the United States shifted to New York, then the second city in the country. Drake and Halleck, two minor poets, calling themselves "The Croakers," issued a series of poems with the principal object of entertaining readers. Drake wrote a fine romantic poem called _The Culprit Fay_. Halleck's best works are the poems on the death of Drake and _Marco Bozzaris_. Washington Irving's chief fame is based on his original creation of the "Knickerbocker Legend" in his _History of New York_, _Rip Van Winkle_, and _The Legend of Sleepy Hollow_. He is an unusually successful writer of short stories, of essays like those in Addison's _Spectator_, and of popular history and biography. He is the first American writer whose works are still read for pure pleasure. Humor and restrained sentiment are two of his pronounced qualities. While the subject matter of his best work is romantic, in his treatment of that matter he shows the restraint of the classical school. His style is simple and easy-flowing but not remarkable for vigor. James Fenimore Cooper's _Leatherstocking Tales_ recreate in a romantic way the life of the pioneer in the forest and the wilderness. The Indian figures more largely in these Tales than in those of any preceding writer. Leatherstocking deserves a place in the world's temple of fame as a great original character in fiction. Cooper is also our greatest writer of stories of the sea. _The Pilot_ and _The Red Rover_ still fascinate readers with the magic of the ocean. The scenes of all of his best stories are laid out of doors. His style is often careless, and he sometimes does not take the trouble to correct positive errors, but his power of arousing interest is so great that these are seldom noticed. His romances are pure, and they inspire a love for what is noble and manly. Irving was almost as popular in England as in the United States, but Cooper was the first American author to be read widely throughout Europe.