The first medal of Sunday's schedule also happened to be the first gold medal ever won by a Kenyan woman in the marathon event, even with the nation's elite standing as a distance-running powerhouse.
Sumgong is only the third Kenyan woman to become an Olympic champion, following wins on the track at the 2008 Beijing Games for Pamela Jelimo (800 meters) and Nancy Jebet Langat (1,500 meters).
World champion Dibaba looked capable of challenging for Olympic gold, too, early on Sunday, but the furious pace-setting of Sumgong ultimately proved too much for her and Kirwa.
Bahrain's Eunice Jepkirui Kirwa won the silver medal nine seconds off the victor, and Ethiopia's Mare Dibaba took bronze, 26 seconds back.
"I just don't know what to say".
"I was scared and thought that he might come and grab us", said Sumgong.
Israel's other representative, Lornah Chemtai Korlima, failed to finish the race.
Linden had to drop out of that race with an injury and this was Cragg's first Olympic Marathon. "I observed her during the morning preparations and saw I alot of determination in her", Kirwa said.
Sumgong, who fell and hit her head in this year's London marathon yet still managed to get up and win, sat in the pack biding her time until the final miles when she began to relentlessly attack in the final 7 kilometers.
Also among the leaders was Kenyan turned Bahrainian pair of Rose Chelimo and Kirwa, Diseree Linden of the United States of America and Kayoko Fukushi of Japan and former race walker Volha Mazuronak of Belarus. Tufa would however limp off at the 18km with what appeared to have been an injured right ankle.
Led by Kirwa, those three runners broke away from a larger pack with less than five miles to go. "I had prepared that I would move out at 35km and my body was responding very well, as well as my movement", explained Sumgong after crossing the line at Rio's Sambadrome.
"In Kenya, we are clean", Sumgong said.