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===Collier's Encyclopedia===

===Collier's Encyclopedia===

Collier's Encyclopedia was a general American encyclopedia published by originally by P.F. Collier and Son, then later by Macmillan.  Described in its preface as "a scholarly, systematic and continually revised summary of the most significant knowledge for humanity", it has long been considered one of the three great contemporary English-language general encyclopedias; this, along with ''Encyclopedia Americana'' and ''Encyclopædia Britannica'', were considered so essential to home learning that the three were sometimes known together as "the ABCs".

Peter F. Collier was a magazine publisher at the end of the 19th century, having made a fortune with his ''Collier's Weekly'' magazine; his publications were known for the excellence of their articles, illustrations, and in many cases the investigative journalism exposing corruption and fraud in high places<ref>https://www.gutenberg.org/files/44325/44325-h/44325-h.htm</ref>. Collier's publishing empire added his encyclopedia in 1902, which over the years would expand its base by being sold door-to-door, with the affordability of paying for and receiving one to two volumes per month.  Meant for high school and college students, it had 20 volumes by 1950; by the time it finished its run in 1997 it had 24 volumes with over 23,000 entries.  The quality of the writing - it had an extensive list of well-known, credentialed authors in its bibliography, and many of its articles were signed - placed ''Collier's Encyclopedia'' alongside ''Encyclopedia Americana'' and ''Encyclopædia Britannica'' as one of the great English language general encyclopedias of the 20th century.

Originally published in 1902, ''Collier's'' expanded its base by being sold door-to-door, with the affordability of paying for and receiving one to two volumes per month.  By 1997 it has 24 volumes with 23,000 entries.

It was realized early on that young people from elementary to high school age benefited from encyclopedias, and the fact that they could be written to their levels of understanding did not escape the notice of the publishers.  ''The Book of Knowledge'' was published by the Grolier Society in 1910, a 24-volume set arranged by topic rather than alphabetically; it would be replaced by the 20-volume ''The New Book of Knowledge'' in 1966, rearranged back to alphabetically. 

 

Other publishers would have their versions printed within a very short time.  ''Compton's Encyclopedia'', a 26-volume work first printed in 1922, had the innovation of a "fact index" in each volume, giving bullet information on subjects not treated elsewhere in the set.  Grolier also published the ''Merit Student's Encyclopedia'' (1967) and the ''Academic American Encyclopedia'' (1980), with all three meant for junior and senior high school students.  Britannica got into the act as well, publishing ''Britannica Junior Encyclopedia'' in 1934, a work in 15 volumes written for elementary school students.

 

By far the most famous of these sets, as well as the best-selling American encyclopedia of any kind, is ''World Book Encyclopedia'', first published in 1918 with 15 volumes, with an expansion to 22 volumes today.  Unlike many other encyclopedias, the World Book is published in volumes that are not uniform from the point of view of length, since each volume covers a specific letter of the alphabet.  The exceptions are C and S which, due to their length are divided into two volumes, while single volumes represent the letters J-K, N-O, Q-R, U-V, and W to Z.  ''World Book'' has a total of 14,300 pages, including about 27,500 photographs or illustrations, with many in color; over 3,800 editors helped write the articles. In the first volume (entries starting with A) the complete list of the main authors and consultants is given, with a synthetic profile and the topics they dealt with. At the end of most of the entries the name of the author is indicated.

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