Kerr shot a four-under 66 for a second consecutive day, while Park carded a five-under 65, leaving both tied for top spot after two rounds at the Royal Mayfair Golf Club.
Both were 8-under 132 in a day of golf under slightly overcast skies with gentle winds.
Kerr, who won the Canadian Open in 2006, said it's a challenging course.
"It's a course where you have to really shape the ball off the tee and be creative," said the 35-year-old American.
"I played very well the last couple of days. It's unfortunate I bogeyed the last hole today, but that's what happens when you hit an errant shot and have to chip out to a difficult pin."
Making par on the par-4 final hole became a longshot for Kerr when she drilled her tee shot into the left rough.
But a bad hole almost became disastrous when the swing on her approach shot was interrupted by the ka-thwam of a nearby spring-loaded portable toilet door.
"I mean, (the noise) really scared me," she said.
"I could have hooked (the ball) in the water."
Kerr was in the same group as Park, the top-ranked player in the world.
The 25-year-old South Korean has won six tournaments on the LPGA tour this year, including three majors.
Earlier this month, the pressure was on when she had a chance at the Women's British Open to become the first golfer to win four majors in a tournament year.
She said the nerves got to her a bit on the Old Course at St. Andrews, and she ended up tied for 42nd.
Park said the time off since then has helped her game in Edmonton.
"I worked on a couple of things after that because I wasn't hitting it my best at the British Open. I'm obviously hitting it a lot better this week and putting a lot better," she said.
"On the greens, I was really comfortable because they're so pure wherever you hit it, it's just going to go right there."
Park followed up five birdies in the first round on Thursday with seven on Friday.
Karine Icher of France logged a four-under 66 to finish tied with American Angela Stanford at one shot back heading into weekend play for the US$2-million purse.
"Good putting made the difference today," said Icher, a 34-year-old seeking her first win on the tour.
"The course is quite hard, (with) tricky fairways and big rough, so I'm looking to get some good drives and putts on the weekend."
Lydia Ko, the defending tournament champion, came into Friday tied for first, but finished the day with Laura Davies and Paula Creamer two shots off the pace.
Ko shot a lights out five-under 65 in the first round, but managed only a one-under 69 Friday.
"I've just got to play my own game and hopefully get some more putts rolling in," said the 16-year-old from New Zealand.
England's Charley Hull, one of the stars of last weekend's European win over the Americans at the Solheim Cup, continued her stellar play.
The 17-year-old from carded a four-under 66 to vault from 20th spot into a four-way tie with Americans Kathleen Ekey, Stacy Prammanasudh and South Korea's Hee Young Park, at three shots back.
"I played pretty solid. I wasn't hitting that good today on the front nine with my tee shots because I felt a little tired out there," said Hull.
"The back nine I got something going, holed a few putts and I'm pretty pleased with that."
Ekey had the best score of the day with a six-under 64, including an eagle on the par-four first hole.
A few of the big names fell by the wayside on cut day.
Stacy Lewis, No. 2 in the world rankings, saw her game blow up in the first round on Thursday. She finished four over par 74 with seven bogeys.
Lewis, from Texas, said she was mentally tired and exhausted from the Solheim Cup loss, and withdrew prior to the start of the second round.
High profile American Michelle Wie said illness played a part in her poor play.
The 23-year-old from Honolulu was six-over 76 Friday for a two-day total of nine-over 149. She said she, too, was hurting from the quick Solheim turnaround.
"I'm completely under the weather. I was struggling today, just could not get out of bed. I just felt really sick today, though that is no excuse," said Wie.
"I'm going to take advantage of the two days I'm not playing, and just not leave my bed and just kind of sleep for 40 hours straight."
Jennifer Kirby, the top Canadian from the first day, couldn't keep the momentum going.
Kirby, from Paris, Ont., began the day tied for sixth, but four bogeys and two double bogeys dropped her to a six-over 76, missing the cut.
"Because I did play really well yesterday and there was a lot of people following our group and stuff like that, I just felt a little uneasy at the beginning," said Kirby.
"I was a little bit nervous and then it was hard to shake after I made a couple of bogeys."
"The top Canadian heading into weekend play will be Samantha Richdale of Kelowna B.C. She was even par both days to sit eight behind the leaders.
Jessica Shepley of Oakville Ont., sits nine behind.
The other 18 Canadians in the field, including Lorie Kane of Charlottetown, missed the cut.