Times were very hard in the early1930s, memorably so. The stock market had fallen by 80% in value, huge numbers of people were unemployed, and the banking system had collapsed. In some countries, dictatorship seemed to be the answer, and there were those in our own country who felt the same way. Fortunately in this never came to pass here, and one of the reasons why it did not was that the government remained in touch with the needs of the people.
In those days, the position of Postmaster General was a political appointment, usually reserved for the head of the President's party. In the 1930s, that person was James Farley a canny politician who perhaps more than anyone else was responsible for the election of Franklin Delano Roosevelt. Farley hit on the idea of using stamps to promote tourism and related businesses.
To this purpose, the ten stamps of the National Parks issue were released in mid-1934. The designs were beautiful and the colors were bright but still muted. Valued simply from one cent to ten cents, the stamps featured national parks in California, Arizona, Washington State, Colorado, Wyoming, Oregon, Maine, Utah, Montana, Tennessee and North Carolina. The images below are all from Wiki Commons except the 8c, from Colnect.com.
Huge numbers of the stamps were issued, consistent with the purpose to promote tourism. They are not at all rare, and can be still be acquired today by anyone at a very low cost, proof again that the esthetic value of a stamp has no relationship to its market price.
Compare the 1934 designs to a recent (2016) National Parks issue. These stamps certainly have nice photographs, but they still look like peal-off stickers, which is exactly what they are, with perforations (the zig-zag lines along the side) added for looks only, with a minor anti-forgery purpose.