2021 WeatherTech 240 at The Glen

[1] The race was a late addition to the 2021 IMSA SportsCar Championship calendar, after travel restrictions related to the COVID-19 pandemic forced the cancellation of the round at Canadian Tire Motorsport Park for the second consecutive year.

On June 30, 2021, IMSA released the latest technical bulletin outlining Balance of Performance for the event.

[3] The lone change occurred in DPi, where the Cadillac DPi-V.R received a one-liter fuel capacity increase after finishing fourth through seventh in class the previous weekend.

[4] Nicky Catsburg, Antonio García, and Jordan Taylor led the GTLM Drivers' Championship with 1082 points, 81 points ahead of John Edwards, Augusto Farfus, and Jesse Krohn followed by Connor De Phillippi, Philipp Eng, and Bruno Spengler in third.

[4] With 1296 points, the GTD Drivers' Championship was led by Bill Auberlen and Robby Foley, ahead of Roman De Angelis and Ross Gunn.

[5] The only change from the previous round in DPi was the absence of Ally Cadillac Racing, while LMP2 saw a reduced three full-season entries after Era Motorsport announced their intention to scale back their 2021 program.

BMW Team RLL's absence saw the return of the three-car GTLM field, while GTD featured a host of changes owing to the round only paying points towards the WeatherTech Sprint Cup.

[7] Gilbert Korthoff Motorsports also made their IMSA SportsCar Championship debut at this event, bringing the GTD class tally to 13.

[8] There was one practice session preceding the start of the race on Friday, taking place on Thursday afternoon.

[9] The first and only practice session took place at 9:20 am ET on Thursday and ended with Olivier Pla topping the charts for Meyer Shank Racing with Curb-Agajanian, with a lap time of 1:48.813, ahead of the No.

3 car for Corvette Racing, besting teammate Nick Tandy in the sister No.

Keating was 0.423 seconds clear of Steven Thomas in the WIN Autosport entry followed by John Farano in the No.

The result kept Filipe Albuquerque and Ricky Taylor atop the DPi Drivers' Championship with 2068 points.

MacNeil jumped from fifth to third while the absent Edwards, Farfus, and Krohn dropped from second to fourth.

[25] GTD drivers, teams, and manufactures did not score full season points due to the event only counting towards the WeatherTech Sprint Cup.