The unicode characters under the "Basic Latin" unicode block from U+0001 to U+007F are the characters that characters we use in English. However, the "Latin-1 Supplement" block from U+0080 to U+00FF is an extension of the "Basic Latin" block and includes characters that are used in some languages. For example, the Spanish language use all the characters from U+0080 to U+00BF as well as the letter "Ñ/ñ" (U+00D1 and U+00F1), which is pronounced like the "ny" in "canyón". So, how did some languages get the characters under the Latin-1 supplement block?
The Latin-1 supplement was taken unaltered from the upper half of an existing standard, ISO 8859-1, which in turn was based on a standard published by the European Computer Manufacturers Association (ECMA) in the early 1980s as ECMA-94.
ECMA-94 was based on an actual hardware encoding, developed by Digital Equipment Corporation (DEC) for its popular VT-220 video display terminal, presumably on the basis of what they perceived as customer demand. But the various national standards associations negotiated some adjustments which, as is often the case, were hammered out in interminable meetings attended by well-meaning people with a lot if enthusiasm but without much expertise in designing character sets.
In the end, ISO 8859 was extended to a series of 8-bit encodings, ISO 8859-1 through ISO 8859-15, providing support for national languages which had not been well-served by the original encoding.
By then it was obvious that 256 codes were not enough for all the alphabets in use at the time, but there was still some reluctance to switch to a wider encoding for languages which could be shoe-horned into eight bits. Many manufacturers were quite prepared to sacrifice the possibility of representing multilingual documents (unless, of course, one of the languages was English), and the relatively simple Unicode proposal was countered within the ISO by a byzantine collection of unworkable multibyte shift encodings. Fortunately Unicode did eventually prevail, but the provisions for context-dependent shift encodings continue to complicate multilingual APIs.
For another view of this history and some interesting links, you can check out the Wikipedia entry on ISO 8859-1.