Knighton repeatedly looked across at the rest of the field as he sprinted down the final straight, and it was Jamaica’s Rasheed Dwyer who finished in second place to join the teenager in the final.
In the second semi-final, Knighton’s compatriot Noah Lyles looked set for victory but leant back on the finish line to come third.
Canada’s Aaron Brown claimed first place and Liberia’s Joseph Fahnbulleh finished second, with the pair and Lyles all recording a time of 19.99. As such, Lyles guaranteed his place in the final as the quickest loser.
In the third semi-final, Andre de Grasse – bronze medalist in the men’s 100m – ran 19.73 to finish first with a Personal Best time, the fastest by any of the semi-finalists.
Kenny Bednarek of the United States also qualified for the final after securing second place behind De Grasse. The 22-year-old clocked the second fastest time of the semi-finals with 19.83.
The field for the final was completed by Jereem Richards of Trinidad and Tobago. Richards was the other quickest loser with a time of 20.10.
There will be no British representation in the final after Team GB’s Adam Gemili pulled up injured in the heats.
Men’s 200m final field
All times taken from semi-finals
Andre de Grasse (CAN) - 19.73 seconds
Kenny Bednarek (USA) - 19.83
Aaron Brown (CAN) - 19.99
Joseph Fahnbulleh (LBR) - 19.99
Noah Lyles (USA) - 19.99
Erriyon Knighton (USA) - 20:02
Jereem Richards (TTO) - 20.10
Rasheed Dwyer (JAM) - 20.13
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies