What state of matter does sound travel the fastest?

Sound travels fastest through matter in the solid state.

I know this from having answered a huge number of questions that required me to look up things like this:

-- Speed of sound in air . . . about 340 m/s

-- Speed of sound in sea-water . . . about 1,500 m/s

-- Speed of sound in steel . . . about 5,960 m/s

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