The H-60 helicopter family which is the U.S. military designation for the Sikorsky S-70 family of helicopters, is the most common U.S. military helicopter, with a wide range of versions and upgrades for different military missions. After the Vietnam War experience, with the UH-1 helicopter being an icon of that war, the United States Army wanted to move to the next generation, requesting proposals, in 1972, for the Huey's successor, termed the Utility Tactical Transport Aircraft System (UTTAS).
First generation Army
As would be expected, the first model was the "A", although there soon were a number of derivatives. Not all the test and special missions, such as Customs Service and VIP transport, are discussed here, just H-60A derivatives with a clear military mission. These were a number of A-model utility transports, many exported, and the EH-60C SIGINT platform with the "Quickfix" emitter location and targeting system.
Second generation Army
The underpowered A models first became the base UH-60L, with an improved engine and transmission.
Medical evacuation versions were the UH-60Q, and the improved HH-60L.
Rather than develop an entirely new helicopter, the Army chose a major mid-life upgrade of the generally successful aircraft. This involves a teardown of A and L models, making fundamental changes to the airframe, electronics and engines. The resulting "M" helicopters (i.e., UH-60M utility, HH-60M medical evacuation, and MH-60M special operations) have comparable performance to the "L" models, but with improved "system interoperability, survivability and sustainability. The aircraft has a fully integrated, digitized, open avionics architecture providing a glass-cockpit, fully coupled flight director, Embedded GPS/INS navigation system, integrated Blue Force Tracker and digital moving map system. The Integrated Vehicle Health Management System (IVHMS) reduces maintenance workload and sets the stage for full implementation of Condition Based Maintenance.
"UH-60M is an “all weather, all terrain, day/night/night-vision-system” vertical maneuver platform critical to the warfight. The Black Hawk delivers 11 combat-loaded troops to a radius of 225 kilometers and can transport an external load of 4,500 pounds to a radius of 135 kilometers, all in “High/Hot” conditions.
"The medical evacuation (MEDEVAC) version of the Black Hawk, HH-60M, includes a full medical evacuation mission equipment package in the cabin area, integrated Forward Looking Infrared Radar (FLIR) and an onboard oxygen generating system."
In the U.S. designation system, the "M" prefix is supposed to mean "special operations". Unfortunately, while most "MH" helicopters of the Army and Air Force are indeed special operations, the Navy MH-60S and MH-60R are general purpose naval helicopters.
Army Special Operations
The first purpose-built Army Special Operations version was the MH-60K, which also can be a major rebuild of the MH-60A. Its primary mission is "overt or covert infiltration, exfiltration, and resupply of special operations forces" at night and in bad weather. To the MH-60A capabilities were added a AN/APQ-174 terrain following radar, more self-protection electronic warfare components, and support for FIM-92 Stinger and AGM-114 Hellfire. It also has a power upgrade of 2 General Electric T700-GE-701C engines.
The MH-60L is a slightly less advanced but cheaper version developed from the UH-60L utility helicopter. 
- HH-60G PAVE HAWK, a CSAR variant with GPS, navigation radar, and defensive avionics
- MH-60G PAVE HAWK, adding FLIR to the HH-60G.
RAST helps a helicopter fuel and land on forward strips and non-carrier warships. It consists of a cable and winch system with components both on the aircraft and surface platform.
- SH-60B Seahawk, navalized with RAST for operation from non-carrier warships; optimized for ASW and ASuW. Offensive radar, magnetic anomaly detector, electronic warfare receivers, and two torpedo/missile pylons.
- SH-60F Ocean Hawk, navalized for carrier operations, adding a dipping sonar that replaced RAST, an extra weapons store, and FLIR.
- HH-60H Rescue Hawk, CSAR based on navalized Seahawk with RAST; no refueling probe but extra tanks.
- MH-60S Knighthawk, utility and mine countermeasures, replacing CH-46 utility, HH-60H Rescue Hawk, MH-53E Sea Dragon mine clearing. .
- MH-60R Seahawk, replacing the SH-60B and SH-60F in the multimission ASW/ASuW.
- SH-60J, a Seahawk with RAST, search radar, additional navigation electronics, searchlight, night vision goggles and no weapons.