What language other than English is most spoken in the US?

The language that is spoken most in the US other than English is Spanish, and it is expected, according to current demographic trends, that eventually Spanish will surpass English as the most spoken language in the US, at which time it may become necessary to make the US officially a bilingual country.

Over 30 million (more than 10%) of the United States population speaks fluent Spanish (2000 census). In fact, with the exception of both Dakotas, Louisiana, Hawaii, Maine, New Hampshire and Vermont, the second most widely spoken language besides English is Spanish.