By 1920 the population of Kissimmee increased to more than 2,700 people as a result of the Florida land boom. In the 1930s the cattle industry began to flourish in the area. However, citrus and other crops remained as the predominant industry. The construction of the Kissimmee Airport in the 1940s by the U.S. Army Corps of Engineers in preparation for the U.S. involvement in World War II caused Kissimmee's population to increase by 38% to 3,700 residents.
City leaders wanting to continue Kissimmee's prosperous history, encouraged growth by attracting retirees to the area during the 1950s. This effort stimulated growth nearly 60%. The next period of growth came in the 1970s with the development of Walt Disney World and other tourist attractions. Since Walt Disney World's debut in 1971, the City's population doubled from 7,500 to 15,000 in 1980. The population doubled again in the 1980s to 30,000.
- 1900 - Electricity comes to Kissimmee. The initial rates were 3 cents per night or $7.50 per month
- 1908 - A Fourth of July celebration was planned to welcome the residents of the new City of St. Cloud. The owner of a new flying school in Kissimmee planned his first flight to highlight the occasion. In taking off, the airplane hit a cow and was destroyed, resulting in the drafting of an air-ship ordinance
- 1915 - Osceola High School plays its first football game, beating Orlando High School 6-0
- 1924 - Kissimmee Chamber of Commerce is chartered
- 1934 - Cattleman's Association is established in Kissimmee
- 1943 - Construction of the Monument of States is completed
- 1944 - The first Silver Spurs Rodeo is held on July 4. Admission is the purchase of one war bond
- 1956 - Record rainfall brings flooding and $2 million in damages to Kissimmee