All of them should be capitalized if they are at the beginning of a sentence. Drive, River, and Railroad would also be capitalized if they are part of proper nouns such as South Drive, Mississippi River, Edaville Railroad.
Yes it should be capitalized.
Missouri river
The Nile River is typically capitalized as it is a proper noun.
St. louise river
Missouri RiverMississippi River
Missouri RiverMissouri River; Illinois River
Yes, it is the name of a place i.e. a 'proper noun'.You should always capitalize a proper noun.
Missouri (and Columbia)
Missouri river
NO. The Missouri river is the tributary
The Missouri River flows into the Mississippi River just north of Saint Louis, Missouri.