Andrew Carnegie (1835-1919) was a Scottish-American steel tycoon and philanthropist. As a businessman he often allowed laborers to work in harsh conditions, which resulted in responses like the 1892 Homestead Steel Strike. As a philanthropist, Carnegie focused on promoting world peace, scientific research, the arts and most notably, public libraries.
In total, he gave away $60 million to help launch 1,689 local public libraries. In order to receive funding, localities had to provide a building site and commit to funding 10% of the construction costs. Additionally, the library was to be kept free.
Carnegie Libraries were distinctive for their focus on open stacks, which allowed people to freely browse content that interested them, without first having to consult a librarian. Separate libraries were built for blacks and whites, respecting segration laws of the time.
All US states except Alaska and Delaware have a Carnegie Library. To this day, the Carnegie Library remains one of the most prominent buildings in many small and medium sized towns in the United States.
For more information, see http://en.wikipedia.org/wiki/Carnegie_libraries.