The Denver Zoo began in 1896 with a single orphaned native black bear gifted to the mayor of Denver. By the early 1900s, Ferril Lake was created using water from the City ditch and the boat pavilion was built. Formal gardens and peaceful carriage-ways were completed as well. 

In 1882, several Sisters of Mercy arrived in Denver from their convent in St. Louis. The Sisters of Mercy founded the 40-bed Mercy Sanitarium in 1901 in the City Park neighborhood. Over the years, the facility was expanded many times until it was closed in 1995 and redeveloped into apartments.

The Colorado Museum of Natural History, subsequently renamed the Denver Museum of Nature and Science, was added on the eastern edge of the park in 1908 and featured an exhibition of bison in a setting of native fauna. 

An electric fountain was added to Ferril Lake in 1908 in time for the National Democratic Convention hosted in Denver. A park employee controlled the 12-water geysers and 11-light beams by manually-moving levers. By the late 1990s, the fountain had fallen in total disrepair. In 2008, in time for the National Democratic Convention hosted in Denver, the fountain was replaced and rededicated. Although similar in shape and size, the $3-million electric fountain has LED-lights and is operated by computer software.

In 1925, the City of Denver selected City Park as the site for replace the former East Denver High School located just east of Downtown. Designed to accommodate 2,130-students, it was intended to be a source of civic pride with its central clock tower of 162-feet. The school was expanded in 1975 and declared a Denver Historic Landmark in 1991.

When City Park first opened, it was a mile away from the city with poor or undeveloped roads. As roads developed and competing trolley companies made it easier for park guests to visit, housing in the area began to develop. Today, the neighborhood contains many historic brick houses and commercial buildings. Denver Squares, Victorians and Bungalows built in the early 1900s are found through-out the neighborhood.