During the 1920s, Bulgaria experienced an economic boom, and trade with the United States began to increase. American firms built grain elevators, dockyards, and dock facilities at the port of Varna. In 1928 Bulgaria was the largest exporter of attar of roses (used to make perfume) to the United States, and also a major exporter of tobacco to the U.S. In 1922 the Bulgarian Finance Ministry made an agreement with the American Banknote Company to print a large quantity of Bulgarian currency in the United States.