Former ASU QB Cleo Lemon was 32 of 44 for 350 yards, but threw three interceptions in the loss.
Hamilton (5-4) moved into a second-place tie with Toronto (5-4) in the East Division with its second straight win over its arch rivals and fourth straight overall for the first time since 1998. More importantly, the Ticats clinched the season series with the Argos, meaning they'll finish ahead of their rivals if the two teams end the regular campaign tied.
Earlier this year, Hamilton had clinched its head-to-head series with fourth-place Winnipeg. So far this season, the Ticats have played just two games against West Division rivals, losing 23-22 to Calgary on July 10 and 37-24 to Saskatchewan on July 31.
But after beating up on both Winnipeg and Toronto, the Ticats are 5-2 within the East Division.
After starting the season 1-4, Hamilton hosts Montreal (6-3) on Saturday. A win would tie that season series 1-1 but also move the surging Ticats into a tie atop the East with the defending Grey Cup champions.
"We had a rough start but that's in the past," Knowlton said. "Now we have Montreal but we're not worried.
"We're going to do what we've been doing and that's playing hard football, going out and getting it done."
Montreal beat Hamilton 37-14 on July 22 in their only previous meeting. Ticats coach Marcel Bellefeuille said posting a winning record within the East is crucial.
"We talked at the beginning of the year about the things we needed to do to be successful and one was win at home and I think we've been accomplishing that," he said. "The second thing was winning the Eastern series because we know it's going to be tight going down the stretch and teams are going to have similiar records and it's going to be important."
Knowlton's block and subsequent touchdown with two seconds left in the first half proved to be the game's turning point. Knowlton led a strong charge up the middle, blocked Jamie Boreham's attempt then was able to chase down the bouncing ball down to give Hamilton a 20-6 half-time lead and the huge momentum shift.
"We had a play called that if it was there to take it," Knowlton said. "It opened up for me and I took advantage of it and blocked it.
"The main thing is to keep your feet and find the ball. When I hit it, I kind of saw where it went so I just kept running."
Toronto head coach Jim Barker said Knowlton's block was just one of many breakdowns of the club's usually sound special teams, with timely penalties often costing the visitors good field position.
The Argos were also their own worst enemy with five turnovers (three interceptions, two fumbles) and three sacks. Starter Cleo Lemon finished 31-of-43 passing for 334 yards and while two of his interceptions ended promising first-half drives Barker wasn't about to pin the loss on his starter.
"Special teams have played well all year but today they let us down," Barker said. "The three interceptions were a large part of it but you can't put it on him.
"It was early in the game when that (two picks) happened."
DeAndra' Cobb and Dave Stala had Hamilton's other touchdowns. Sandro DeAngelis booted three converts and two field goals while Eric Wilbur added a single.
Ticats' starter Kevin Glenn was pretty solid, completing 27-of-33 yards for 313 yards with a touchdown and an interception.
CFL rushing leader Cory Boyd had Toronto's touchdown but only had 11 carries for 54 yards. Grant Shaw kicked a convert and two field goals.
Knowlton provided the first half's biggest plays but it was a staunch Hamilton defence that helped stake the Ticats to their half-time lead.
Three times Toronto drove into the red zone but could only manage a field goal. Lemon drove the Argos to the Hamilton 14-yard line, but that drive was snuffed out by a Geoff Tisdale interception late in the first to preserve a 7-3 Ticats' advantage.
Then in the second, Lemon and Co. were on the Hamilton 10-yard line before Jerome Dennis's interception in the end zone ended that threat to keep it a four-point contest.
"Those were big-time," Knowlton said. "We understood he (Lemon) had problems with certain reads and were able to take advantage of that."
Added Boyd: "You don't want mistakes when you get down there. You have to make the plays but we didn't do that as much as we wanted to."
Hamilton also executed a successful fake punt in the quarter. Wilbur went six yards on third-and-two as part of an 11-play, 53-yard drive that culminated in a 23-yard field goal at 13:54 for a Ticats' 13-6 lead.
A successful challenge by Bellefeuille set up Hamilton's first TD. A completion and fumble by Toronto's Chad Lucas had originally been called an incompletion, but Bellefeuille's challenge gave Hamilton the ball at Toronto's 49-yard line.
Four plays later, Cobb's one-yard run opened the scoring at 2:51 to cap a 61-yard, four-play drive that was helped mightily by unnecessary roughness and pass interference penalties that totalled 47 yards.