Answer:
The correct answer is relationship era.
Explanation:
The economic history of the United States has its roots in the European settlements of the 16th, 17th and 18th centuries. The American colonies progressed from marginally successful colonial economies to 13 small independent agricultural economies that joined in 1776 to form the United States of America. In 230 years, the United States grew into an immense, integrated and industrialized economy that accounts for more than a quarter of the world economy. The main causes of its expansion were the existence of a large unified market, a political-legal support system, vast areas of highly productive agricultural land, large natural resources (especially wood, coal and oil) and an entrepreneurial spirit and commitment to invest in material and human capital. The economy has maintained high peaks, attracting immigrants by millions from around the world. Technological and industrial factors also played an important role.