After his graduation, he took up the management of his father's large estate in Westchester County, New York, and also studied law at Albany. Poor eyesight soon compelled him to give up the legal profession. He early became interested in various philanthropic enterprises and reforms and identified himself especially with the temperance, antislavery, and antiwar movements. He was one of the founders of the American Bible Society, which he defended against the vigorous attacks of the High Church party, led by Bishop John H. Hobart. He was Judge of Common Pleas in New York from 1818 to 1820, and was first judge of Westchester County from 1820 to 1842, when he was removed on account of his anti-slavery views. An enthusiastic member of the American Anti-Slavery Society, whose constitution he drafted, Jay stood with James Birney at the head of the conservative abolitionists, and by his calm, logical, and judicial writings exerted for many years a powerful influence. From 1835 to 1837 he was the society's corresponding foreign secretary. In 1840, however, when the society began to advocate measures which he deemed too radical, he withdrew his membership, but with his pen he continued his labor on behalf of the slave, urging emancipation in the District of Columbia and the exclusion of slavery from the territories, though deprecating any attempt to interfere with slavery in the states. He was also a proponent of antiwar theories and was for many years president of the Peace Society. His pamphlet War and Peace: the Evils of the First with a Plan for Securing the Last, advocating international arbitration, was published by the English Peace Society in 1842, and is said to have contributed to the promulgation, by the powers signing the Treaty of Paris in 1856, of a protocol expressing the wish that nations, before resorting to arms, should have recourse to the good offices of a friendly power.
Personal life
In 1812, Jay was married to Augusta McVickar, the daughter of John McVickar, Esq. of New York. Together, William and Augusta were the parents of eight children, all but two who survived to adulthood. Their children included:
According to Frederick Douglass, Jay "was our wise counsellor, our fine friend, and our liberal benefactor." Lewis Tappan described him as "one of the most talented and useful abolitionists in this country, who, by his pen and active labours, has performed a greater service to the cause than perhaps any other man".
