Seward was born in southeastern New York, where his father was a farmer and owned slaves. He was educated as a lawyer and moved to the Central New York town of Auburn. Seward was elected to the New York State Senate in 1830 as an Anti-Mason. Four years later, he became the gubernatorial nominee of the Whig Party. Though he was not successful in that race, Seward was elected governor in 1838 and won a second two-year term in 1840. During this period, he signed several laws that advanced the rights and opportunities for black residents, as well as guaranteeing fugitive slaves jury trials in the state. The legislation protected abolitionists, and he used his position to intervene in cases of freed black people who were enslaved in the South.
After many years of practicing law in Auburn, he was finally elected by the state legislature to the U.S. Senate in 1849. Seward's strong stances and provocative words against slavery brought him hatred in the South. He was re-elected to the Senate in 1855, and soon joined the nascent Republican Party, becoming one of its leading figures. As the 1860 presidential election approached, he was regarded as the leading candidate for the Republican nomination. Several factors, including attitudes to his vocal opposition to slavery, his support for immigrants and Catholics, and his association with editor and political boss Thurlow Weed, worked against him and Abraham Lincoln secured the presidential nomination. Although devastated by his loss, he campaigned for Lincoln, who was elected and appointed him Secretary of State.
Seward did his best to stop the southern states from seceding; once that failed, he devoted himself wholeheartedly to the Union cause. His firm stance against foreign intervention in the Civil War helped deter the United Kingdom and France from entering the conflict and possibly gaining the independence of the Confederate States. He was one of the targets of the 1865 assassination plot that killed Lincoln, and was seriously wounded by conspirator Lewis Powell. Seward remained loyally at his post through the presidency of Andrew Johnson, during which he negotiated the Alaska purchase in 1867 and supported Johnson during his impeachment. His contemporary Carl Schurz described Seward as "one of those spirits who sometimes will go ahead of public opinion instead of tamely following its footprints".
Seward was born in on May 16, 1801, in the small community of Florida, New York, in Orange County. He was the fourth son of Samuel Sweezy Seward and his wife Mary (Jennings) Seward. Samuel Seward was a wealthy landowner and slaveholder in New York State; slavery was not fully abolished in the state until 1827. Florida was located some 60 miles (97 km) north of New York City, west of the Hudson River, and was a small rural village of perhaps a dozen homes. Young Seward attended school there, and also in the nearby county seat of Goshen. He was a bright student who enjoyed his studies. In later years, one of the former family slaves would relate that instead of running away from school to go home, Seward would run away from home to go to school.
At the age of 15, Henry—he was known by his middle name as a boy—was sent to Union College in Schenectady, New York. Admitted to the sophomore class, Seward was an outstanding student and was elected to Phi Beta Kappa. Seward's fellow students included Richard M. Blatchford, who became a lifelong legal and political associate. Samuel Seward kept his son short on cash, and in December 1818—during the middle of Henry's final year at Union—the two quarreled about money. The younger Seward returned to Schenectady, but soon left school in company with a fellow student, Alvah Wilson. The two took a ship from New York to Georgia, where Wilson had been offered a job as rector, or principal, of a new academy in rural Putnam County. En route, Wilson took a job at another school, leaving Seward to continue on to Eatonton in Putnam County. The trustees interviewed the 17-year-old Seward, and found his qualifications acceptable.