In trying to sort out what Mac hardware supported which operating systems and what new features, it became useful to create a chart to help visualize it. Since I didn't have a current copy of OmniGraffle handy at the time, I made a 1920×1080 slide in Keynote! That was 2012; I have regularly updated it since then.
Macs that can run macOS Mojave (10.14) and Catalina (10.15) are shown with black text descriptions; Macs that can not upgrade past macOS High Sierra (10.13) are shown with brown text; Macs whose terminal OS is El Capitan (10.11) are shown with green text (you'll need to check the second page to find those). You can use the icons along the top (placed chronologically) to see what the minimum version of macOS is that you can use on each Mac (generally, the one that it shipped with). The chart also marks the earliest machines in each line that support AirDrop, AirPlay Mirroring, Bluetooth 4.0, Handoff (and a number of other features listed on the Legend page that require the same minimum hardware), Auto Unlock, and 10-bit Colour (a.k.a. Deep Color, 1 Billion Colours). If you need specific details, may I suggest Mactracker (another Made in Canada/Alberta product!) or Apple Tech Specs. Note that Education-only models do not appear in the chart. The Xserve line is similarly omitted.
For a full-size view of the chart and additional pages with a Legend and Mac models back to 2006, download the PDF version. You can also click/tap on the item name/icon in the PDF version to go to the related Apple Tech Specs page on the Apple Support web site.
Updated 2020-05-07 to add the 2020 MacBook Pro 13" models.
Prior to 2020, this page was posted and maintained on the University of Calgary Integrated Arts Media Labs web site.