Conversation so far:
What was the Colorado River Storage Act of 1956?
Called for the creation of other irrigation projects and several large dams, including the Glen Canyon Dam in Utah, which created Lake Powell.
Was the Colorado River Storage Act bill easy to pass for Wayne N. Aspinall?
In '55, Aspinall conceded that for the bill to pass, he needed to sacrifice the Echo Park plan. Several more compromises between the two sides gave way.
Was Wayne N. Aspinall eventually able to get the Colorado River Storage Act bill to pass through Congress?
The bill passed the House 256-136 in March 1956 and then-President Dwight Eisenhower signed it into law soon thereafter.
What was Wayne N. Aspinall political position during 1956?
Member of the U.S. House of Representatives from Colorado's 4th district
Why did the people oppose the Colorado River Storage Act?
The Colorado River Storage Project became a volatile issue between environmentalists and water project advocates. because of increased environmental awareness around the country, the majority of the public opposed the project
Is there anything else significant about Wayne N. Aspinall's role in the Colorado River Storage Act besides passing the bill?
In 1954 alone, the Department of the Interior received 20,000 pieces of mail about the plan, and one insider estimated the letters ran 80 to 1 in opposition of the project.

Question: What were the nature of the mail received?
Self-contained rewrite: What were the nature of the mail received?