The last OS update the first-generation iPad received was iOS 5.1.1, released just over two years after the first-generation iPad was released.
The first-generation iPad was a bit of an odd case for software updates, though (due to insufficient RAM); every other iPad has gotten at least four or five major updates before losing support. And Apple has yet to drop support for any iPads from the iPad Air on (October 2013).
The first-generation iPad was a bit of an odd case for software updates, though (due to insufficient RAM); every other iPad has gotten at least four or five major updates before losing support. And Apple has yet to drop support for any iPads from the iPad Air on (October 2013).