Region Exclusive: Tauros
As like the Mainstream Pokemon Games where some Pokemon are exclusive to a given Version of a Game, so something similar is found within Pokemon GO. Instead, however, a handful of Pokemon are exclusive to a given region or country in the world. Within the 1st Generation of Pokemon GO, there are four different Pokemon that are Region Exclusive.
One of those four Pokemon is tauros, who is exclusive to players only found in North America. But there's a catch... Instead of being found everywhere in North America, Tauros can only be found north of the Latitude Line of 29. This means that Tauros is found everywhere in North America OUTSIDE of the south portion of Florida and the far southern tip of Texas. During the 1st Generation of Pokemon GO, this was known as the Tauros Line. However, with the addition of the 2nd Generation, this cutoff was deemed the Tauros/Heracross Line since the Pokemon known as Heracross can only be found below this given latitude.
Since Trading has yet to be incorporated in Pokemon GO, the only realistic way of obtaining tauros is by visiting this greater portion of North America. Sometimes there may be given events that are held which will see certain Region Exclusive Pokemon being found in other areas of across the globe, but said events are unpredictable. It was also once believed that a player could find Region Exclusive Pokemon of other countries in Pokemon Eggs, but that concept has since been deemed impossible.