Collier's Encyclopedia is a U.S. encyclopedia. It was first published in 20 volumes in 1950-51 and in 1962 was expanded to 24 volumes. It can be considered one of the three major contemporary English-language (printed) encyclopedias, together with Encyclopædia Britannica and Encyclopedia Americana. The United States of America — also referred to as the United States, the U.S.A., the U.S., America, the States, or (archaically) Columbia—is a federal republic of 50 states located primarily in central North America (with the exception of two states: Alaska and Hawaii). ... 1913 advertisement for Encyclopædia Britannica. ... 1913 advertisement for the 11th edition, with the slogan When in doubt - look it up in the Encyclopædia Britannica The Encyclopædia Britannica (properly spelt with æ, the ae- ligature) is the oldest English-language general encyclopedia. ... The Encyclopedia Americana is a reference work targeted at young teenagers (grade 8 in the US Educational system). ...

The 1997 edition had 23,000 entries. There are not many short entries, as related subjects are usually consolidated in longer articles. A high percentage of the illustrations are in color. Bibliographies are found in the last volume rather than at the end of articles. The last volume also contains the essential index with 450,000 entries (1997 edition). A CD-ROM version was first published in 1996. An annual Collier's Year Book is also published.