Residents are encouraged to display a blue light in their home or office windows during the holiday season to remember fallen law enforcement officers.

State Police Commissioner Frank Noonan issued a reminder today about "Project Blue Light," a program developed by Concerns of Police Survivors, a nonprofit organization based in Missouri that represents more than 15,000 families of officers killed in the line of duty.

The tradition started in 1988, when Dolly Craig wrote to the group and said she would be putting blue candles in her living room window that holiday season to honor her son-in-law, Daniel Gleason, who was killed in the line of duty while serving with the Philadelphia Police Department.

"The color blue is symbolic of peace," Noonan said. "By displaying blue lights, you will show that you support America's law enforcement officers. Any police officer passing by it on some dark, cold winter's night will be warmed by the kindness it implies."

Noonan said 93 members of the Pennsylvania State Police have been killed in the line of duty since the department's founding in 1905.