She was the wife of Harry T. Moore, who founded the first branch of the National Association for the Advancement of Colored People (NAACP) in Brevard County, Florida.

The murder of the Moores was the first assassination to happen during the Civil Rights Movement and the only time both a husband and a wife were killed for their activism.

Simms taught elementary school classes for many years in Merritt Island and Mims in Brevard County, and in Lake Park, Florida until her death.

Renewed attention was brought to the case by a 1999 biography of Moore, describing him as the first civil rights martyr, and a 2000 PBS program about his life and legacy.

Some, like the Moores, were activists, but most were either people who had refused to bow to racist convention or simply "innocent bystanders, unsuspecting victims of random white terrorism.

Supplemented by independent funding, by 2004 the county had created the Harry T. and Harriette Moore Memorial Park and Interpretive Center at the homesite in Mims.

In 1999, journalist Ben Green published a book based on his research of the case, Before His Time: The Untold Story of Harry T. Moore, America's First Civil Rights Martyr.

On August 16, 2006, Crist announced the results of the work of the state Office of Civil Rights and the Florida Department of Law Enforcement.

Based on extensive evidence, the state concluded that the Moores were victims of a conspiracy by members of a central Florida Klavern of the Ku Klux Klan.