Which of the following US cities had a population over one million in 1860

The diversity of the nation’s cities was nowhere more on display than in the nation’s largest city, New York. At the turn of the twentieth century, New York City was the national capital of finance, industry, shipping and trade, publishing, the arts, and immigration, a magnet that drew to it much of the best and most avant-garde in art and literature. With a population of more than three million in 1900 and 4.7 million by 1910, New York was more than twice as populous than Chicago, the nation's second-ranked city, three times as large as third-ranked Philadelphia, and six to nine times as large as St. Louis, Boston, Baltimore, and Cleveland, all urban centers of immigrants.^4  

4

start superscript, 4, end superscript

Explanation:

a.

congress passed laws allowing for free passage between states.