Sites which offer information about occupations with an eye toward completing genealogies are linked to from here.
Regular Websites
A. Philip Randolph Pullman Porter Museum
Built and named in honor of this African-American pullman porter, the museum and its agency focuses ob railroad history and is helpful in the research of those who worked as porters. - A. Philip Randolph Pullman Porter Museum
http://www.aphiliprandolphmuseum.com/
Provides a detailed history of its history, including photographs, research, and databases. - Circus Historical Society
http://www.circushistory.org/
The official database of the United States Patent and Trademark Office contains every one of the more than 6 million patents issued since 1790. - USPTO Patent Database
http://www.uspto.gov/patft/