The names of some places, such as "El Salvador", "El Cairo" or "La Haya" always include the article (just as "The Hague" does in English). For some others you can optionally add the article, the RAE lists several examples here:

             http://buscon.rae.es/dpdI/SrvltGUIBusDPD?lema=el

(el) Afganistán, (el) África, (la) Argentina, (el) Asia, (el) Brasil, (el) Camerún, (el) Canadá, (el) Chad, (la) China, (el) Congo, (el) Ecuador, (los) Estados Unidos, (la) India, (el) Líbano, (el) Pakistán, (el) Paraguay, (el) Perú, (el) Senegal, (el) Uruguay, (el) Yemen, etc

In any case, whenever the article is optional the most common form omits it (and in fact most of these examples sound terrible to my ears, even though they are occasionally heard).

The names of some places, such as "El Salvador", "El Cairo" or "La Haya" always include the article (just as "The Hague" does in English). For some others you can optionally add the article, the RAE lists several examples in the page about the definite article "el".

(el) Afganistán, (el) África, (la) Argentina, (el) Asia, (el) Brasil, (el) Camerún, (el) Canadá, (el) Chad, (la) China, (el) Congo, (el) Ecuador, (los) Estados Unidos, (la) India, (el) Líbano, (el) Pakistán, (el) Paraguay, (el) Perú, (el) Senegal, (el) Uruguay, (el) Yemen, etc

In any case, whenever the article is optional the most common form omits it (and in fact most of these examples sound terrible to my ears, even though they are occasionally heard).