[4] In 1789, he engaged in the business of marine insurance, often for ships involved in the kidnapping and sale of African people through the trans-Atlantic slave trade, and accumulated a large fortune.

[5] He kept with his own hand very accurate accounts, a rare thing in those days, and made it a rule never to borrow money, never to engage in speculation of any kind, and never to take more than the legal rate of interest.

He was at different times a member of both branches of the legislature, of the first Boston City Council, and of the Massachusetts Constitutional Convention of 1820–1821.

Mr. Brooks gave liberally, and without parade, to many benevolent objects, and, besides this, his private donations for many years exceeded his domestic expenses.

[12][13] Brooks' fourth great-grandson, Dr. Patrick Graves Jackson, is the husband of Supreme Court Justice Ketanji Brown-Jackson.