Cities in the Rhine Franconian dialect Area speak West Central German dialects .
Frankfurt is the largest city in the Rhine Franconian dialect area ( Franconian dialects ) .Frankfurt was a city state , the Free City of Frankfurt , for nearly five centuries , and was one of the most important cities of the Holy Roman Empire , as a site of imperial coronations ; it lost its sovereignty upon the collapse of the empire in 1806 and then permanently in 1866 , when it was annexed by the Kingdom of Prussia .
Frankfurt