He introduced concessions to the national parks. Among the services they sold were basic amenities and necessities to park visitors, plus aids for studying nature. Mather promoted the creation of the National Park to Park Highway. He also encouraged cooperation with the railroads to increase visitation to normally remote units of the National Park System. He believed that once more of the public had visited the parks and enjoyed a comfortable stay in concessionaire facilities then they would become supporters for the fledgling agency and its holdings. By the time he left his position, the park system included 20 national parks and 32 national monuments. Mather also had created the criteria for identifying and adopting new parks and monuments.