There were several. Keep in mind that wrestling eligibility has had four eras - 3 years until WWII, 4 years from 1947 until the late '50s or early '60s, back to 3 years and then the current 4 years. I don't have a complete list, but here are some. From Oklahoma State, pre-war: Earl McCready, Jack Van Bebber, Rex Peery and Joe McDaniel. In the early '60s period The Cowboys had Yojiro Uetake Obata. Bill Koll is an interesting case. He won all of his matches his sophomore year at ISTC, but enlisted in the army before the NCAA tournament. He then came home from the war and won 3 titles. There are probably more, and I may do some research later.
Coincidentally, Wrestling for Life is partnering with Joe McDaniel's daughter, Mary Jo, on a program to get wrestling shoes to kids and schools that need them.
Quick - (no Googling) - who was the first true freshman to win an NCAA title?