Alsatian is a Germanic language spoken mainly in Alsace, a region in north eastern France which has passed between French and German control many times during its history. As a result Alsatian has been influenced a great deal by the French language.
Alsatian belongs to the Alemannic group of the Upper German branch of the West Germanic language family. The name Alemannic comes from the Alamanni, an confederation of Germanic tribes first mentioned by the Romans in 213 AD and conquered by the Franks in 496 AD. Various forms of this name are used for Germany in a number of modern languages, including French (Allemagne), Turkish (Almanya), Portuguese (Alemanha) and Welsh (Yr Almaen).
Alsatian is not easily intelligible to speakers of standard German, but is closely related to other Alemannic languages, such as Swiss German and Swabian.
Wikipedia puts the number of Alsatian speakers at 1.6 million, but Omniglot show only about 96,000, 60% of the inhabitants of Alsace. The majority of speakers are adults and only about 36% of primary school pupils can speak the dialect. There is limited usage Alsatian in the media: one radio station, Radio France Alsace, broadcasts in Alsatian and other radio and TV stations broadcast some programs in the dialect.
Many speakers write in standard German, although street names, which were formerly only in French, may use local spellings.
Sources:
Wikipedia
http://www.getalsaced.com/alsatian-language.html