Thaddeus Stevens was a native of Vermont; however, he is most known for the work he did in the state of Pennsylvania. Stevens was born on April 4, 1792, in Danville, Vermont, to Joshua Stevens, a shoemaker and surveyor, and Sarah Morrill. Thaddeus Stevens was raised mostly by his mother after his father left the family when young Thaddeus was twelve years old. His mother took very special care of her second son Thaddeus because he was born with a club foot, which he was especially conscious of for the rest of his life. His mother recognized his superior intelligence and provided her son with a good education by taking care of their family farm and by working as a nurse. In 1807, his mother moved the family to Peacham, Vermont, so that Stevens could attend the Peacham Academy, which was also known as Caledonia Grammar School. After graduating from Peacham Academy in 1811, Stevens enrolled at Dartmouth College in New Hampshire. Stevens graduated from Dartmouth in 1814, and after hearing about the opportunities in Pennsylvania from a friend and former student at Dartmouth, Stevens moved to York, Pennsylvania.

In 1815, Thaddeus Stevens arrived in York, Pennsylvania, and he was hired as a school teacher at the York Academy. Stevens came to Pennsylvania to practice law, not to teach, and he was admitted to the bar in 1816. After receiving his license to practice, Stevens opened his own firm in Gettysburg, Pennsylvania. At first, Stevens did not receive many cases, but after he helped a suspected murderer plead insanity, he became a very popular lawyer in the area. While his firm continued to grow, so did his assets, especially since he was investing in real estate throughout Adams County. Stevens also invested in the iron business with a partner and owned the Maria Furnace and the Caledonia Forge both in Adams County.

His true political career started in 1829, when he first started his attacks on Free-Masonry. Thaddeus Stevens claimed that the Free-Masons were conspiring and monopolizing the positions in government. In 1833, he was elected on the Anti-Masonic ticket as a State Representative to the Pennsylvania General Assembly; he served in this position for nine years. While Stevens was in office, he was aggressive in his proposals to curb secret societies, specifically Free-Masonry. He aimed to get larger amounts of money for Pennsylvania colleges, to defend the public tariff on the United States Bank, and to abolish slavery. During his years in office, many state works programs were extended; however, he was most known for the "Tapeworm Railroad" and the "Buckshot War" of 1838. The "Tapeworm Railroad" was established to provide jobs and transportation, even though it zigzagged (hence the name tapeworm). Many of Stevens's opponents claimed that the railroad was built so that he could make money through his iron business by supplying the tracks. The "Buckshot War" occurred when there was a divide between the Pennsylvania Assembly; Stevens, along with two other assembly members, were forced to escape from a mob through a window. It was called The "Buckshot War" because the militia sent in to control the mob was restrained with 13 rounds of buckshot. Stevens did many great things for the State Commonwealth of Pennsylvania.

Thaddeus Stevens was a strong supporter of public education and defended the adoption of a law providing free public schools in 1834. Even though he had no part in passing the law, he was one of the sole people to defend the law when it seemed certain that it would be repealed. Stevens withdrew from the public spectacle in 1842 after he did not receive an appointment to William Henry Harrison's cabinet. Stevens moved to Lancaster and started a new law practice. Unfortunately, he was in debt due to his involvement in the iron business.

Stevens sold much of his property to Gettysburg College to pay off his debt, and then he decided he wanted to return to politics. In 1848, Stevens was elected as a Whig to Congress from Lancaster County. When the Whig party collapsed, he became a member of the new Republican Party. Stevens was made chairman of the House Ways and Means Committee, which handled all of the finances for the Union. Stevens was a leading figure on the Joint Committee for Reconstruction and also helped to pass the Fourteenth and Fifteenth Amendments. He also led the movement to impeach Andrew Johnson. Thaddeus Stevens was one of Johnson's first critics and opponents. Stevens, along with many other "Radical-Republicans," felt that Johnson was impeding their Reconstruction plans. Stevens took charge of the movement to impeach Johnson. The attempt to impeach Johnson was unsuccessful after the Senate failed to convict him on charges of violating the Tenure of Office Act.

The final act he introduced was a bill that tried to establish free schools in the District of Columbia. At the age of seventy six, Thaddeus Stevens passed away on August 11, 1868, in Washington, D.C. After his death, his body was laid in the Capitol Rotunda. Stevens was then buried at Shreiner's Cemetery in Lancaster, Pennsylvania.