The afternoon had looked set to be a vibrant affair as Town fans turned up in their straw boaters to celebrate promotion to the Championship.
But the atmosphere fell strangely flat as Luton failed to create clear chances despite dominating possession.
Nevertheless, the win coupled with a draw for second-placed Hull now leaves the Town five points clear of the Tigers with just three games remaining.
Steve Howard fired a 25-yard effort at visiting keeper Matt Baker after just 15 seconds and Peter Holmes was next to see a 15-yard effort saved four minutes later as Town started brightly.
A neat interchange between Ahmet Brkovic and Kevin Foley then saw Howard beat Baker to the full-back's cross only to see his header clip the top of the crossbar from eight yards in the fifth minute.
But Luton's early upbeat tempo then died off until Town went ahead after half-an-hour when Kevin Foley crossed and Chorley sent a diving header past his own keeper for an own goal.
The visitors had their first effort on goal in the 33rd minute when Dean Lewington whipped in a cross from the left and Wade Small powered a 14-yard header goalwards only for Marlon Beresford to adjust his body and superbly tip the ball over the bar.
Luton almost grabbed a second when Underwood crossed for Howard to direct a header just past the post from 10 yards in the 52nd minute.
But the game degenerated into a scrappy affair as play was broken up by constant fouls and infringements.
Howard had another header just wide in the 78th minute and substitute Enoch Showunmi was denied by a fine Lewington tackle as he raced clear at the death.