Keystone City

 Keystone City is a city located across the Missouri River from Central City, in Kansas. Keystone City and its sister-city are known as the "Twin Cities" due to their proximity to each other; separated only by a river that runs between them. The city has been described as "the blue collar capital of the United States" and a center of industry.

Keystone City first became home to settlers in 1806, shortly after the Louisiana Purchase. It began to grow rapidly after the Civil War, attracting farmers and becoming a common starting point for those who were moving to the West. After the completion of the Transcontinental Railroad, it became an important depot, attracting the livestock and meat-packing industries. Although the stockyards closed in the 1950s, the area has been revitalized and the old warehouses transformed into a fashionable retail destination. Keystone remains a center of industry, home to aircraft and automobile manufacturers.

The Thinker, the Fiddler, and the Shade put the city in suspended animation for years until it was discovered and freed by Barry Allen.

Trivia

 * Keystone City first appeared in Flash Comics #1 (January 1940)
 * Due to the reality-altering effects of Crisis on Infinite Earths, Central City gained a twin city named Keystone City. Originally, Keystone City was located on the parallel Earth known as Earth-Two, in approximately the same space where Central City was located in Earth-One. Following the Crisis, both cities appeared alongside each other.
 * Keystone was the home of Jay Garrick, the original Flash.