The E-2 Hawkeye came out of the Navy's need for an Airborne Early Warning Aircraft. It was the first plane designed from the wheels up for that role. It was also able to be integrated into the Navy's Tactical Data System. This enabled it to act as a command and control aircraft as well.
I actually thought this was a relatively new aircraft but it first flew in 1960 after some difficulties on the part of Grumman. The Navy wanted a plane that could fly off the older Essex carriers as well. As it turns out, it never did. That meant that Grumman had to cram a ton of electronics in a smaller airframe. The plane reached operation capacity in 1964.
The current version is the E-2D with more powerful electronics and engines.