Luton boss John Still hailed a "phenomenal" all-round effort as Cambridge's 2-0 defeat at Kidderminster handed them the Skrill Premier title and a return to the Football League.
Tuesday night's loss for the U's means they are now 10 points behind Luton with three games remaining.
A delighted Still told www.lutontown.co.uk: "It's overwhelming for me but I'm just so pleased for everyone who has worked so hard and supported this club so long.
"This is for everyone associated with this club that has gone through hell over the past few years.
"This is a fantastic time to be associated with this club. The supporters deserved it. They have been simply sensational.
"All the players and staff, plus those behind the scenes, have been phenomenal. I tip my hat to them."
Goals from Harriers duo Amari'i Bell and Michael Gash ended Cambridge's title challenge and means they have to settle for a play-off place in their bid to play League football next season.