The Blues had offered Pronger $7.22 million, rather than risk losing him to free agency after this season.
"Chris has been a great player for us," said Blues General Manager Larry Pleau of Pronger's 10 seasons. "He's been a workhorse, logs a lot of ice time, played through injury."
However, Pleau said, Pronger's desire for a long-term contract "was something we couldn't do."
The 6-foot-5 defenseman said every Canadian kid dreams of playing at home, but it will be difficult leaving the Blues.
"I have a lot of great friendships from here, I met my wife here and I grew up from a little boy to a man, really maturing in front of everybody's eyes here. I'll miss it," Pronger said. "I'm an Oiler now."
Beautician charged with giving client fatal silicone butt injection
Astronomers offer more expansive view of universe