The 25-year-old was competing in the very first race of Day 10 of the championships when she breezed past the line in the new world record of 12.12, breaking the previous mark of 12.20 by 0.08 seconds.
After the race, Amusan spoke about how it felt to break the record, while still staying focused on the upcoming final.
"It is a strong feeling," she said. "I wanted to get out and go. I did what I had to do. Looking forward to the finals."
In the final, she did not disappoint. The Nigerian burst out of the blocks to set an even faster time of 12.06, albeit with an illegal tailwind.
However, none of that would have mattered for the new world record holder who walks away from these championships with a gold medal and the fastest time in history.
Just a day ago, Amusan had set a new African record with a time of 12.40 in the heats. Now she has added a world record and gold to her resume in impressive fashion in Oregon.
After the final, an ecstatic Amusan talked about how she had fulfilled every goal she had set for herself at these Worlds.
"The goal was to come out and to win this gold," she said. "I just did it.
"Honestly, I believe in my abilities but I was not expecting a world record at these championships. You know, the goal is always just to execute well and get the win. So the world record is a bonus.
"I knew I had it in me but I could not believe it when I saw it on the screen after the semis. But it was just a matter of time.
"And I am thankful. Before the final, I just tried to stay calm and to do my best. I took a deep breath knowing that I have some goal to accomplish and it worked pretty good. I knew it was very fast but not this fast."