In just over 12 hours, United Launch Alliance will be launching their Delta IV rocket in it's "Medium" configuration consisting of a 4-meter fairing and 2 solid rocket boosters strapped to the sides of the main booster. After this launch, only the Delta IV Heavy rocket will launch from the Delta family of rockets, once those are done the Delta rockets will be retired as a whole. The Delta Heavy has 5 more launches after this, with the last launch being NROL-70 from Cape Canaveral, FL in 2024.
The 27-minute launch window opens at 9am EDT, with the live broadcast starting at 8:40am EDT which can be viewed here. Liftoff will occur from Space Launch Complex37 at the Cape Canaveral Air Force Station in Florida.
The payload on this mission is GPS III, a satellite for the US Air Force which will be 3x more accurate than any other GPS satellite ever launched. It has enhanced anti-jamming software on board that ensures signals do't get interrupted when being used during important communications.