Electricity made development of effective units possible. In 1901 American inventor Willis H. Carrier built was is considered the first modern electrical air conditioning unit In 1902 he installed his first air-conditioning system, in the Sackett-Wilhelms Lithographing & Publishing Company in Brooklyn, New York; his invention controlled both the temperature and also the humidity which helped maintain consistent paper dimensions and ink alignment at the printing plant. Later, together with six other employees Carrier formed The Carrier Air Conditioning Company of America, a business which in 2020 employed 53,000 employees and was valued at $18.6 billion.