During about a hundred years after the thirteen English colonies on the east coast of North America had won their independence from England and emerged as the United States of America, that country had attained its present territorial proportions. The westward territorial expansion of the United States took place at the cost of the American Indian tribes which inhabited those areas.

The American Indians resisted these encroachments, but by 1890 this resistance finally ended in a massacre at a place called Wounded Knee in South Dakota. USA also purchased the vast territories of Louisiana and Alaska from France and Russia respectively, and seized Texas and California from Mexico after a war with that country.

Between 1861 and 1865 there was a civil war, when the southern states of USA, which were primarily agricultural with plantations worked by slave labour, seceded from the Union. As a result of the defeat of the southern states in the civil war, the Union was preserved and slavery was abolished. Within about three decades after the end of the Civil War, USA had become the foremost industrial power in the world.

By the end of the nineteenth century, she was producing about one-third of the total production of iron and steel in the world. In almost every branch of industry, she outstripped every other country in the world.