in 1849, 1855, and 1861, the last time as a Democrat, and served from March 4, 1843, until his death in 1862. In the Senate, Pearce served for nineteen years as chairman of the Committee on the Library (Twenty-ninth through Thirty-seventh Congresses). According to Benjamin Perley Poore, Pearce, while "a brilliant conversationalist and a welcome guest at dinner," also "shrank from political controversy," a disposition reflected in his management of the Committee on the Library:[D]uring his long service on the Committee having it [the Library of Congress] in charge he selected the books purchased. In doing this he excluded all works calculated in his opinion to engender sectional differences, and when the Atlantic Monthly was established he refused to order it for the Library.Pearce also served in 1861 for two months as chairman of the Committee on Finance. In 1847–1862, he served as a member of the Executive Committee of the Regents of the Smithsonian Institution. He was involved with the United States Coast Survey, which was among the oldest United States Government scientific organizations, and the United States Botanic Garden. In the U.S. Senate, Pearce became known as an erudite and pragmatist. In 1850, he developed the so-called Pearce Plan, a part of Compromise of 1850. The Pearce Plan provided a solution for the boundary dispute between Texas and the Federal government. Pearce wrote a bill that granted Texas $10 million in compensation for agreeing with the state borders charted by the government. After being approved by Congress, the bill was signed by President Millard Fillmore. In 1850, President Fillmore offered Pearce, first, to become a judge of the United States District Court for the District of Maryland, and then, — Secretary of the Interior. Pearce chose to stay in the Senate. The Whig Party having become fragmented after Henry Clay's death, Pearce joined the Democratic Party in 1856 and supported James Buchanan's nomination for presidency. During the sectional crisis Pearce stood against the dissolution of the Union. However, he was hesitant to discuss the slavery issue being a slaveholder himself. After the Civil War broke out, he did not resign. In March 1862, he appeared in the Senate for the last time. Pearce died in Chestertown on December 20, 1862, and is interred in New Chester Cemetery. His deathbed from the Hynson-Ringgold House was preserved and now exhibited in the historic Geddes-Piper House (c. 1770) in Chestertown, Maryland.