Some won't consider Hill's to be the HS record as she's a pro (but we don't get why a pro invalidates the fact you are still in HS) but the old HS record was Francena McCorory's 36.96 from 2006. Hill did not beak McCorory's US junior mark of 36.67.
If you wonder why our sport isn't popular, watch the video of the race.
It takes a lot of knowledge for the sport to be truly exciting. An American and US HS record get broken and yet it's no different really than watching the 5th heat of a JV 300 from a specatator viewpoint, except for the time.