People gathered Monday for a memorial service celebrating Dr. Denton Cooley, one of the leading pioneers of modern heart surgery.

Dr. Cooley died Nov. 18 at the age of 96. His memorial service was held at Trinity Episcopal Church in Midtown.

Dr. Cooley pioneered many techniques in cardiovascular surgery and saved countless lives throughout his storied career. He performed the first human heart transplant in the United States in 1968.

Cooley and his wife, Louise, were married nearly 70 years and had five daughters, 16 grandchildren and 17 great-grandchildren.