"It's good to be back, obviously, in No. 1 spot," said Park, who has had to overcome hand and back injuries over the last couple of seasons. "That really wasn't my goal playing this year; just came as (a) present. So it's great.
"I mean ... all the rankings are so close together. It can change every week. It's just hard to keep track. I'm just trying to play golf, and doesn't matter where I am at."
Olympic champion Park needed to finish sixth or better to have a shot at recapturing top spot.
She shot a three-under-par 68 in the final round at Wilshire Country Club to finish tied with compatriot Ko Jin-young in second, two shots behind winner Moriya Jutanugarn of Thailand.
Park, who entered the final round seeking her second win of the season, uncharacteristically missed a few fairways and a number of birdie putts on Sunday.
The 29-year-old has spent a total of 92 weeks atop the world rankings during three different stretches between 2013 and 2015. Her last stint was a 19-week run that ended in October 2015.
(Reporting by Frank Pingue in Toronto; Editing by Peter Rutherford)
