Richland's transformation from a small farming community to a nationally significant city began during World War II.

In 1943, the federal government selected the area surrounding Richland as part of the Manhattan Project, the top-secret program created to develop the world's first atomic weapons. The location was chosen because of its remote setting, access to abundant water from the Columbia River, available electrical power, and favorable climate.

To make way for the project, the federal government acquired the Town of Richland and surrounding lands. The original community was dissolved, and a new planned city was rapidly constructed to house the thousands of scientists, engineers, construction workers, and support personnel arriving from across the country.

Richland became one of the nation’s first master-planned communities. Distinctive neighborhoods, schools, parks, churches, and commercial districts were developed to support the growing population. Many of the city's well-known Alphabet Homes were built during this period to provide housing for workers and their families.

The Hanford Site played a critical role in producing plutonium used during World War II, including material used in the Trinity Test and the atomic bomb dropped on Nagasaki, Japan. Following the war, Hanford continued to support national defense efforts throughout the Cold War.

The Manhattan Project and Hanford era profoundly shaped Richland’s physical layout, economy, and culture. Today, many historic sites, neighborhoods, and community landmarks continue to reflect this unique chapter in American history.