Beginning in the 1870s, American men of all classes were united in their passion for?

Baseball

Explanation:

In the decades following the Civil War, Americans underwent striking changes in their everyday life. Sports became a popular pastime for many Americans in the late nineteenth century. Baseball became one of the games that drew enormous crowds from all classes together. Many games occur in America, but baseball remained a comforting and steady sport for the people. Eventually, baseball became the national game of America.