When did U.S. consuls first receive a salary?

An Act of Congress of August 18, 1856 established two schedules of consular posts. Consuls appointed to Schedule B posts were paid between $1,000 and $7,500 per year. They could still collect fees, but could no longer engage in trade. Schedule C appointees received between $500 and $1,000 per year and could engage in trade. Non-citizens might be appointed to consular posts, but could not be paid.