During the 1950s, an increase in the number of marriages and births fueled a demand for housing.
People who was born in the 1950s were known as the baby boomers. The increasing number of marrieages and births in population of post-World War II led to an increase in the demand for housing and gave rise to higher density cities.
By the 1970s, the United States economy had grown by leaps and bounds and was by far the largest economy in the world.
If you meant that question literally then the answer is the America got all his land mostly by the battle of independence from Great Britain in which it got all the territory that the british took or claim after the french-indian war in which france and the british sign a treaty which stated that all territory gain from battle most be return. In which the british later =send a huge debt to the 13 colonies that stated that they most pay for all the damage done thanks to the french and indian war