Historical information on which versions of Android were in use is hard to come by. The authoritative source of information is Google's Android developers dashboard but that lacks historical information. There is a graph on Wikimedia commons which shows the changes over time and has links for many of the data points.
We have gone through and made a spreadsheet of all this information along with citations for each value. This is also available as a CSV file.
Google also publishes some additional information about build numbers and code names.
The graph was last updated with data for May 2019 but the spreadsheet and CSV file are updated monthly.
