1 What problem led to playgrounds becoming more common in
American cities?

William Joseph Simmons  was the founder of the second Ku Klux Klan.

Explanation:

Inspired by The Birth of a Nation, Col. William J. Simmons (May 6, 1880 - May 18, 1945), a preacher, and promoter of fraternal orders, led a cross burning on Stone Mountain, on Thanksgiving night 1915, that marked the beginning of a new era of Ku Klux Klan activity.

The Ku Klux Klan employed terror in pursuit of their white supremacist agenda. One group was founded immediately after the Civil War and lasted until the 1870s. The 19th-century Klan was originally organized as a social club by Confederate veterans in Pulaski, Tennessee, in 1866. They derived the name from the Greek word kyklos, from which comes the English “circle”; “Klan” was added for the sake of alliteration and Ku Klux Klan emerged.

In August 1925, 40,000 of its members marched in front of the White House.