It was William Lassell who first discovered Triton. The British astronomer actually discovered Triton just a few weeks after the discovery of Neptune. A self-made telescope was used in order to discover this moon. This is Neptune’s largest moon after all so it is not surprising that this is the first one that was discovered.
As more powerful tools and equipment started to come up in the latter years, more and more moons of Neptune have been discovered. Neptune has 13 moons all in all. The retrograde orbit of Triton has always been considered a good thing by a lot of astronomers and those who are enthusiastic about the solar system.