Generally speaking, you should not use an article with a proper noun unless the proper noun has a prepositional phrase. A prepositional phrase are words like: of, in, on, and under. Proper nouns such as Berkley or Louisiana will not need an article because there is no prepositional phrase.
Proper nouns like the United States of America will need an article because there is a prepositional phrase in the name. Use a definite article when referring to geographical terms: the Nile, the Empire State Building. Also use a definite article when referring to the plural—the Great Lakes, the Galapagos Islands.