Montgomery Blair

Blair graduated from the United States Military Academy in 1835, but after a year's service in the Seminole War, he left the Army, studied law, and began practice at St Louis, Missouri, in 1839. In 1836, he married Caroline Rebecca Buckner of Virginia. After her death in 1844, he married Mary Elizabeth Woodbury, daughter of Levi Woodbury. After serving as United States district attorney (1839–43) and as judge of the court of common pleas (1834–1849), he moved to Maryland in 1852 and devoted himself to law practice principally in the United States Supreme Court. He was United States Solicitor in the Court of Claims (1855–58) and was associated with George T. Curtis as counsel for the plaintiff in the Dred Scott v. Sandford case of 1857.

While the Blairs, as a family, were often characterized as conservative on the issue of slavery, Blair notably served as the defense counsel for Dred Scott when the enslaved African-American took his case to the Supreme Court in 1857. Scott was the slave of an Army doctor, John Sanford (the name was misspelled in the official record) who had taken his servant along for prolonged stays in free territory. On Scott's behalf, Blair argued that the time the black man had spent in the free state of Illinois and in Minnesota, free territory since the Northwest Ordinance of 1787, made him a free man. The ruling by Court's majority against Scott's right to freedom is often cited as one of the contributing causes of the Civil War. Writing for the majority, Chief Justice Roger Taney affirmed that the black man had no rights "that the white man was bound to respect" and that black slaves could not be considered American citizens despite having been born in the U.S. This landmark decision was denounced as a step toward the "nationalization" of slavery by Lincoln and others opposed to the expansion of that institution. Conservative as he may have been on other aspects of the slavery issue, Blair's work in the case of Dred Scott vs. Sandford suggests a willingness to embrace more progressive viewpoints.

The Blairs, like many other nationalist Democrats but, unusually for politicians from the border states, had abandoned the Democratic Party in the wake of the Kansas–Nebraska Act and had been among the founding leaders of the new Republican Party. Four years after Blair switched political parties, President Buchanan removed Blair from his position of United States Solicitor in 1858. In 1860, Blair took an active part in the presidential campaign on behalf of Abraham Lincoln. After his election, Lincoln appointed Blair to his cabinet as Postmaster General in 1861. Lincoln expected Blair, who advocated taking a firm stance with the southern states, to help balance more conciliatory members of his cabinet. While Postmaster-General, Blair instituted a uniform rate of postage and free delivery in cities. Blair also began the sale of money orders by post offices to reduce the mailing of currency to reduce post office robberies. He also called for the First International Postal Conference, which was held in Paris in 1863 and began the process that led to the Universal Postal Union.

Differing from the Republican Party on the Reconstruction policy, Blair gave his adherence to the Democratic Party after the Civil War, along with his brother, who was the Democratic vice presidential candidate in 1868.

In 1876, Blair was counsel to Secretary of War William W. Belknap during the House of Representatives investigation into the Trader post scandal and requested the House Investigation Committee chaired by Hiester Clymer to drop the charges against Belknap if the latter resigned office. Clymer, however, declined Blair's offer. Belknap was impeached by the House of Representatives for receiving illicit payments from the Fort Sill trader post on the Western frontier while Secretary of War. Belknap had been given sole power by Congress to choose sutlers to operate lucrative trader posts that sold supplies to U.S. soldiers and Indians. Belknap resigned over the scandal and was acquitted in a Senate trial during the summer of 1876. Many senators did not believe that Congress could convict a private citizen, but the Senate passed a resolution that stated Congress could convict a private citizen.

In 1882, Blair unsuccessfully ran for U.S. Representative from Maryland's sixth district.

His 600-acre (2.4 km) manor in present-day Silver Spring, Maryland was named Falkland. It was burned by Confederate troops during their thrust towards Washington, D.C. After several years afflicted with "inflammation of the spinal membranes," he died at Silver Spring on July 27, 1883. The funeral services were held at Rock Creek Church, and he was buried at Rock Creek Cemetery. In memory of Blair, the United States Post Office closed on July 30, 1883.