Ebenezer Hoar was born in Concord, Massachusetts, on 21st February, 1816. After graduating from Harvard University in 1835 he was admitted to the bar in 1840.
Hoar worked as a lawyer in Boston, was a member of the Whig Party and in 1846 was elected to the State senate. A leader of the anti-slavery Whigs, Hoar refused to support Zachary Taylor when he became the party's presidential candidate in 1848. Hoar helped form the Free Soil Party but eventually becoming a member of the Republican Party.
In 1869 President Ulysses S. Grant appointed Hoar to the post of U.S. Attorney General. He soon upset the Senate by insisting that the nine newly created federal judgeships be filled according to merit rather than by patronage. The Senate obtained its revenge by refusing to confirm Hoar when Grant nominated him for a seat on the Supreme Court.
Hoar resigned as Attorney General in 1870 and resumed work as a lawyer in Boston. He served in the House of Representatives (1873-75) but retired from active politics after being defeated in his attempts to be elected to the Senate in 1876.
Ebenezer Hoar died in Concord, Massachusetts on 31st January, 1895.