What are the reasons for the rapid economic rise of the United States after the 197s?

The Civil War maintained national unity, abolished black slavery, and further cleared the obstacles to the development of capitalism; Establishing the advanced system

the promotion of the second industrial revolution;

expand territory and develop the west;

excellent conditions: abundant resources and broad market; The international bad environment is superior and less affected by war; A large number of immigrants, providing labor and technology

colonial activities in Latin America and the Pacific, with strong economic and technological strength,