Surtz finished in 5 minutes, 9.07 seconds, more than two seconds ahead of runner-up Lydia Roller of Staunton.
Surtz expected a faster pace.
"All my coaches said I'd have to break five [minutes] to win," she said. "I was a little bit surprised, but the weather's different. It was really windy and hot."
Surtz missed much of the spring's cold, wet weather because of the shin splints, which she said were caused by a growth spurt.
The layoff had her wondering how the postseason would go, and also changed her menu of events.
"I wasn't sure how I'd do," she said. "I've been cross-training a lot, so that's been really great."
Still, she believed focusing on the 1,600 — and not running the 3,200 — was the best course.
"I didn't know how long it'd take to get back down to shape," Surtz said.
But running a 5:05 at the Kane County Meet gave her the confidence that a state title was a realistic goal.
Surtz also joined freshman Katie Ubertino and sophomores Katie Lifka and Maia Italia on Rosary's fourth-place 3,200 relay team.
Italia, Melanie Meyer, Julie Bottarini and Annie Molenhouse teamed to take fifth in the 1,600 relay. Surtz's win and the two relay finishes were enough to help Rosary tie for ninth with 18 points.