Interesting note, as of today, the US is the first country to have successful spacecraft missions visit all of the classical planets.
There is one big exception, of course: the Soviet Union was the first to have a spacecraft visit Earth, with Spunink.
This category is completely arbitrary, especially given that Pluto is now considered a minor planet. Still, it's an achievement of note.
Mercury - 1974, Mariner 10
Venus --- 1962, Mariner 2
Earth --- 1957, Sputnik 1
Mars* --- 1965, Mariner 4
Jupiter - 1973, Pioneer 10
Saturn -- 1979, Pioneer 11
Uranus -- 1986, Voyager 2
Neptune - 1989, Voyager 2
Pluto --- 2015, New Horizons
* The Soviet Union launched several probes to Mars before the US did, but those probes failed. This may be true of other planets as well.
edit: formatting
There is one big exception, of course: the Soviet Union was the first to have a spacecraft visit Earth, with Spunink.
This category is completely arbitrary, especially given that Pluto is now considered a minor planet. Still, it's an achievement of note.
* The Soviet Union launched several probes to Mars before the US did, but those probes failed. This may be true of other planets as well.edit: formatting