The first Scott catalog was a thin 21-page pamphlet with the grand title Descriptive Catalogue of American and Foreign Postage Stamps, Issued from 1840 to Date, Spendidly Illustrated with Colored Engravings and Containing the Current Value of each Variety. It was published in September 1868 by J.W. Scott, an early stamp dealer in New York, and purported to list all the stamps of the world and giving prices for each. The fine print of the inside does caution the excited buyer that "it is simply impossible for any one to always have every stamp" in stock.
In subsequent years, the Scott company gave up dealing in stamps, but continued to publish the catalog, gradually providing more and more detail as the hobby evolved and collectors became more sophisticated. In addition to the factual information about the stamps, the catalog also includes price information which is based on market analysis and reported sales from the previous year. As of 2002, and despite annual changes to save space, the catalog was over 5,000 pages.
The Scott numbering system is copyrighted, and the company regularly acts against anyone who uses it without permission in any way other than to publish price lists.
As the dominant catalog in the US, Scott editors have great influence over what is and is not considered to be a valid postage stamp. For instance, in the 1960s the countries of the United Arab Emirates issued many stamps that were likely never actually on sale in a post office, so Scott does not list them. One must go to a Michel catalog to see them described. The lack of a Scott listing, though, means that most American dealers will simply refuse to traffick in such stamps.
The original catalog has been reprinted, and has generally been available from Scott. Scott Publishing Co. was acquired by Amos Press, Inc.