These are difficult questions. One answer can be found at [[Wikipedia:Database reports/Templates with the most transclusions]]. On April 22, the generic Infobox template [[Template:Infobox]] was transcluded on 566,270 pages. This counts both direct and indirect transclusions. Most infoboxes use this template; unfortunately, some of the most common don't. The two most common specific infobox templates are [[Template:Infobox Settlement]] (202k uses) and [[Template:Taxobox]] (155k uses). Neither of these use [[T:Infobox]], as you can check for yourself by clicking on "edit"/"view source", and checking the list of transcluded pages at the bottom. The database report on transclusions is kept up to date by a bot twice per month. You have to check for yourself at which date certain infoboxes started using [[T:Infobox]]. Older data is difficult to obtain. You may be able to parse database dumps of the entire wikipedia, to see how many articles contain the string "{{Infobox" or "{{Taxobox". (I think taxoboxes are the only common infoboxes that don't have a name starting with "Infobox".) The oldest infoboxes predate [[T:Infobox]], and even templates themselves; they will be very hard to count. The earliest infobox I found was at [[Beryllium]], on 2 Feb 2002. It wasn't called "Infobox" then, of course, but it certainly was one. Eugene