Route 758
From Bulbapedia, the community-driven Pokémon encyclopedia.
Route 758 is the location that PokéPark took place in, in Nagoya, Japan.
There was a contest to name the street PokéPark was to be built in to give it a location in the Pokémon game world. There were 2,203 entrants, and "Route 758" was the winner.
In Japanese, phone numbers are sometimes given as mnemonics derived from alternate pronunciations of the digits - for example, one such mnemonic for 262816 might be furo ni hairō. One possible mnemonic for 758 is nagoya, from nanatsu go yattsu, and it is possible this was the reason the name was chosen.
It is unclear if this will have any affect on the games if it eventually does reach 758 routes, which, following the current pattern of numbered routes, may happen during Generation IX, if the region in question has more than 57.

