Les prépositions géographiques

Source: http://french.about.com/od/geography/French_Geography.htm

Les pays

When trying to determine which preposition to use with a country or continent, the only difficulty is in knowing its gender.

Nearly all countries that end in e are feminine and the rest are masculine. There are just a few exceptions:

le Cambodge
le Mexique
le Mozambique
le Zaïre
le Zimbabwe

All continents end in e and all are feminine.

Once you know the gender, it is a simple matter to decide which preposition to use. Masculine and plural countries take à or de plus the appropriate definite article (le, la, or les). Feminine countries and continents take en or de, no article.

Country is:	To or In	From
masculine	au / à l'	du / de l'
feminine	en	de / d'
plural	aux	des

Examples:

Masculine country	Feminine country	Plural country	Continent
Je vais au Danemark.	Elle va en France.	Il va aux Etats-Unis.	Tu vas en Europe.
Je suis au Danemark.	Elle est en France.	Il est aux Etats-Unis.	Tu es en Europe.
Je suis du Danemark.	Elle est de France.	Il est des Etats-Unis.	Tu es d'Europe.

Les villes et les îles

Unlike the other geographical names, the gender of an island or city does not affect which preposition must be used.

The prepositions à and de (or d') are always used with cities and singular islands, while aux and des are used with plural islands.

	To / In	From
city or singular island	à	de / d'
plural islands	aux	des

Examples:

City	Singular Island	Plural Islands
J'habite à Paris. Je suis de Paris.	Je vais à Hawaï. Je suis d'Hawaï.	Je vais aux Îles Cook. Je suis des Îles Cook.

Les états

In order to decide which preposition to use with an American state, you must first determine its gender, which is a matter of memorization: all but nine states are masculine.

Masculine states can be preceded by either dans le or au to mean to/in, and du to mean from unless they start with a vowel (see 2, below).

Exceptions: dans/de l'état de New York, dans/de l'état de Washington: these are said this way to distinguish between the cities and the states by the same name.
Masculine states that start with a vowel can take either en or dans l' for to/in, and d' or de l' to mean from. Example: Arizona (m): en Arizona/dans l’Arizona, d’Arizona/de l’Arizona
All feminine states take en (to, in) and de (from).

	Meaning
State/Province is:	To or In	From
masculine and starts with consonant	dans le / au	du
masculine and starts with vowel	dans l' / en	de l' / d'
feminine	en	de

Examples:

Masculine	Feminine	Exceptions
Je vais dans le Nevada.	Je suis en Floride.	Je travaille dans l'état de New York.
Il est du Québec.	Elle est de Géorgie.	Il est de l'état de Washington.
Nous sommes en Illinois.
Es-tu d'Arizona ?

Here are the 50 US states as said in French. Most states are masculine; only the nine in italics are feminine.

Alabama	Alaska
Arizona	Arkansas
Californie	Caroline du Nord
Caroline du Sud	Colorado
Connecticut	Dakota du Nord
Dakota du Sud	Delaware
Floride	Géorgie
Hawaï	Idaho
Illinois	Indiana
Iowa	Kansas
Kentucky	Louisiane
Maine	Maryland
Massachusetts	Michigan
Minnesota	Mississippi
Missouri	Montana
Nebraska	Nevada
New Hampshire	New Jersey
l'état de New York*	Nouveau-Mexique
Ohio	Oklahoma
Oregon	Pennsylvanie
Rhode Island	Tennessee
Texas	Utah
Vermont	Virginie
Virginie-Occidentale	l'état de Washington*
Wisconsin	Wyoming

*These are said this way to distinguish between the cities and the states with the same name.