Thomas Law entered East India Company service in 1773 as a clerk and rose to revenue administration in Bihar. He combined fiscal duties with judicial and executive responsibilities and proposed more predictable land revenue. His ideas contributed to debates leading to the Permanent Settlement under Lord Cornwallis. He also acquired a fortune through trade before returning to England because of ill health in 1791.

Law emigrated to the United States in 1794 and invested in land and buildings in the new federal capital. His purchases linked him with the speculative ventures of James Greenleaf and other developers, exposing him to falling values, litigation, and financial difficulty. He backed commercial development near the Anacostia and advocated a canal connecting it with the Potomac. An anonymous pamphlet in 1804 promoted the canal as a means of drawing trade to Washington, and he became an incorporator of the Washington Canal Company.

He also supported a theater, learned societies, and economic development. Writing as Homo, he advocated a national paper currency and public measures to stimulate production. After the burning of Washington in 1814, he supported retaining the capital there and helped provide temporary accommodation for Congress. His household also connected him with the Washington family through his 1796 marriage to Elizabeth Parke Custis, which later ended in separation and divorce. He continued writing and investing despite the erosion of his fortune.