The 12,600-pound Asian elephant was born at the zoo on April 14, 1962, The (Portland) Oregonian reported.
At that time, Packy made international news, as he was the first elephant born in the United States in 44 years.
"Suddenly, Portland had something to both shout and gloat about and the city -- no, make that the entire state -- literally quivered with anticipation," wrote veterinarian Matthew Maberry, who assisted in Packy's birth, in his memoir about the event, titled "Packy and Me." "Nothing like this had happened in Portland's history [or world history, for that matter]."
Packy was born to Belle and Thonglaw. Between 1975 and 1983, he sired seven calves of his own.
The zoo holds an annual party for Packy, but as this year marks a half century in his life, zoo staff plan on making it extra special, the report said.
The party starts Saturday at 10 a.m. with music, games and activities that will last all day. Cake will be served to both guests and Packy later in the day.
At 2 p.m. Packy will be knighted by the Royal Rosarians.