"We only use proper names with a stressed definite article when the person is famous or when we doubt his identity in spite of knowing his name, as in Are you THE Bill Hunter?, implying that there may be different persons of the same name but one is better known than the others. . . .
"The situation is different with geographical names, or toponyms, which are notorious for their seemingly unsystematic use: some have no article, others have the definite article. Whether a geographical name is used with or without a definite article is often a matter of historical accident. . . .
"The names of most countries such as Canada take no article, which reflects their conceptualisation of a clearly bounded political entity. Countries or geographical areas that are seen as collections of political units take a plural proper name with the definite article, as in the United States, the Netherlands, and the Baltics.
"A clear instance of a semantic opposition between the zero-article form and the definite article is found in the names of Referral Marketing Video states such as Ohio and names of rivers such as the Ohio. States are clearly bounded political entities, while rivers are natural phenomena that may stretch for hundreds, even thousands of miles so that we do not have their overall extension in mind. Most river names, therefore, require the definite article to mark an unbounded entity as a unique referent."
(Günter Radden and René Dirven, Cognitive English Grammar. John Benjamins, 2007). Developers FAQs