At first, the US Air Force was not interested in a Multirole F-15, because it was very successful in the air, so that it was not needed to upgraded it´s air to ground capabilities. However, even despite of a lack of official interest, McDonnell Douglas started developing a Multirole F-15, with the aim to replace the F-111 Strike fleet and the remaining F-4 Phantom aircraft.
In the 1970s the Enhanced Tactical Fighter program was initiated by the US Air Force, so that McDonnell Douglas was wanted by General Wilbur Creech ro use it´s concept in the program, which was later renamed to "Dual Role Fighter" (DRF) program. Primarly, the aim of the program was to find a replacement for the F-111 Aardvark, but the main reason might be that Wilbur Creech was worried about the F-117 Nighthawk. Even if the F-111 had a long operational history, the DRF study wanted to built more F-111F, but later it was decided to use the F-15E Strike Eagle.
In that timeframe McDonnell Douglas modified a TF-15A, the costs for that were company funded. This prototype was first flown on 8th July 1980. After that the US Air Force contracted a competition in that the F-15E Strike Eagle competed with the strongly modified F-16XL. Even if the F-16XL showed great performance, the F-15E Strike Eagle was declared as the winner on 24th February 1984. The reasons for that were the conventional design of the Strike Eagle (less risk) and the higher surviveability (two engines instead of one).
The first flight of a definitive Strike Eagle was on 11th December 1986, the first aircraft were sent to the US Air Force on 12th April 1988. Until 2001 the US Air Force received 237 F-15E.