Officer Robert Keller was shot and killed on the night of October 5, 1967 while he was responding to a burglary alarm that went off at a dress shop on Pacific Boulevard.
Keller, a Navy veteran who had been with department for only a year, was shot in the chest and died of his injuries.
His daughter, Adreena Briggs, was only 5 months old.
"Unfortunately, that meant my entire life, I grew up without my dad," she said. "It caused us to lose my dad and I didn't have my dad my entire life. I've always felt like he was a hero. My dad felt that defending our country and helping the citizens of this wonderful town was important."
The Huntington Park Police Department held Monday's ceremony at Robert Keller Park, which honors Keller's life and service and serves as a place where one can remember the department's first fallen officer.
The police department and the Rio Hondo Police Academy posthumously honored Keller with a pride run and by rededicating the park next to city hall in Keller's name.
Meanwhile, a $20,000 reward is being offered to anyone with information that will lead to the arrest and conviction in Keller's death.
"The main thrust of this will be the examination of evidence with new technologies to enhance the profiles of the evidence that we have," said Los Angeles County Sheriff's Department Det. Joe Purcell.
Briggs hopes someone will come forward with information to help solve the case, which would hopefully give her some closure.
"It's so fabulous and special to me that all these police officers at this police department are also calling my dad a hero," she said.
Anyone with information can contact homicide investigators at 323-890-5500.