The son of Jonathan Andrew, a farmer and storeowner, and Nancy Green Pierce, a schoolteacher, John Andrew was born in Windham, Massachusetts (in the part of the state that became Maine in 1820). He attended Bowdoin College and graduated in 1837. He moved to Boston, where he entered the law and became active in politics. An idealistic lawyer, devoting much of his early career to pro bono work for prisoners and blacks, he made a name for himself fighting fugitive slave laws. He considered the abolitionist John Brown a hero and arranged for his defense counsel after Brown was caught at Harpers Ferry in 1859. In politics he was active with the “Young Whigs,” an antislavery splinter group that became the Free-Soil Party. He served a term in the Massachusetts legislature (1857).
During the 1860 elections Andrew was the head of the Massachusetts delegation ...