Carl Linnaeus invented the index card in order to help deal with the information overload facing early scientists that occurred from overseas discoveries. Linnaeus had to deal with a conflict between needing to bring information into a fixed order for purposes of later retrieval, and needing to integrate new information into that order permanently. His solution was to keep information on particular subjects on separate sheets, which could be complemented and reshuffled. In the mid 1760s Linnaeus refined this into what we call index cards. Index cards could be selected and moved around at will to update and compare information at any time.
[4]
Until the digitization of library catalogs, which began in the 1980s, the primary tool used to locate books was the
card catalog, in which every book was described on three cards, filed alphabetically under its title, author, and subject (if
non-fiction). Similar catalogs were used by law firms and other entities to organize large quantities of stored documents. However, the adoption of standard cataloging protocols throughout nations with international agreements, along with the rise of the Internet and the conversion of cataloging systems to digital storage and retrieval, has made obsolescent the widespread use of index cards for cataloging.
The first early modern card index was designed by Thomas Harrison (ca 1640s). Harrison's manuscript on The Ark of Studies
[5] (Arca studiorum) was edited and improved by
Vincent Placcius in his well-known handbook on excerpting methods (De arte excerpendi, 1689). Using cards to create an index was the brainchild of 18th-century naturalist
Carl Linnaeus, who is known as "the father of modern taxonomy" for his work on categorizing species. For organizing data, he needed a system for that was expandable and able to be rearranged easily; so he kept each datum on an individual sheet, and could add new sheets and reorganize simply.
Card catalogs as currently known arose in the 19th century, and
Melvil Dewey standardized the index cards used in library card catalogs in the 1870s.
In the late 1890s,
edge-notched cards were invented, which allowed for easy sorting of data by means of a needle-like tool. These edge-notched cards were phased out in the 1980s in favor of computer databases, and they are no longer sold.
Kardex index card filing system
James Rand, Sr.'s Rand Ledger Company (founded 1898) with its Visible Ledger system, and his son
James Rand, Jr.'s
American Kardex dominated sales of index card filing systems worldwide through much of the 20th century. "Kardex" became a common noun, especially in the medical records field where "filing a kardex" came to mean filling out a patient record on an index card.
[6]
photo: Coach Stotts of the Portland Trailblazers of the National Basketball Association, known as one of the most organized coaches in the history of the league, shown here utilizing Index Cards as quick reference of offensive sets, scouting report data and his player’s names. 
