Map O.1 Use of aggregated cellphone records to track mobility week by week during COVID-19 lockdowns in The Gambia, March–May, 2020 http://bit.do/WDR2021-Map-O_1 ...

If you want to get technical about it, the first Pokémon game to have multiple maps was Gold & Silver. After you beat the Johto Elite Four, you could then take on the Indigo League over in Kanto.