In French, why do we say " dans le Montana," but "en Virginie"?

Answer 1

Salut....
In french, we use "en" to delineate a Country, or Continent.
(en Europe, en France) There is an exception of Canada. They say "Au Canada".
Regarding USA, we say : Aux Etats Unis. We say "en Floride".
Name Montana means mountain and some times they use "dans" to express a feeling of "inside mountain" .No specific rule....
Even the Russians say "On Ukraine" , for it's the biggest state in the former USSR. (HA UKRAUHE).
Now, there is not a matter of masculine or femminine, but a set patter/pattern about it.
If you post the whole sentence, I may be able to give you a more detailed opinion!
Amitie's......
Ciao.......John-John.

Answer 2

Chevalier was on the right track.

Generally speaking, masculine state names tend to require the preposition/definite article combo "dans le," whereas feminine state names are preceded by the preposition "en."

However, there are enough exceptions and special cases to warrant a detailed list of which preposition to use with which state name. The link below will take you to such a list.

Answer 3

Montana: masculin
Virginie: Feminin