Volume thirteen of the Correspondence of James K. Polk documents a critical juncture in the history of North America. The eleventh president’s letters from August 1847 to March 1848 reveal his and his correspondents’ official and personal concerns during the final months of the Mexican War.

The U.S. capture of Mexico City and the Treaty of Guadalupe Hidalgo redrew the continental map. Mexican land stretching from Texas to California became part of the United States. Including the earlier settlement of the northwestern boundary with Canada, Polk’s policies had enlarged his country by one-third. Governing the new land proved a challenge. At odds over whether to allow slavery west of Texas, Congress, to Polk’s annoyance, could not unite on a bill to form territorial governments. Some began to fear that discord over slavery’s expansion would split the nation in two.

Polk faced other crises and opportunities during this period. Letters discuss treaty negotiations with the Kingdom of Hawaii, Mormons’ journey from Illinois to the Salt Lake Valley, U.S. interest in annexing Cuba, and the opening of diplomatic relations with the Papal States. Dakota leaders sought the president’s help in conflicts with other Indians and with U.S. officials. European revolutions prompted hopes in America, including by Polk, for the spread of republican government. 1848, too, was an election year. Though some Democrats urged Polk to reconsider his pledge not to seek reelection, he let others vie for the party’s nomination. Ominously, a split within the party in New York over slavery threatened any Democrat’s chance of retaining the White House.

Polk corresponded with the famous and the obscure. This volume includes letters by Abraham Lincoln and Nathaniel Hawthorne-and by female seminary students and a purveyor of patent medicines. Herein Americans mourn the late John Quincy Adams, a Catholic bishop praises Polk’s religious tolerance, and ordinary Americans weigh in on slavery and war. The president found time to write to friends and family and to monitor his private business. Of particular interest to him were the work of the slaves on his Mississippi plantation and the construction of the Nashville home where he and his wife, Sarah, looked forward to retiring.

These are but a sampling of the many topics addressed in Polk’s letters. Presented here with full annotation, they illuminate American politics, diplomacy, economy, and culture.