Category link: https://commons.wikimedia.org/wiki/Category:Ordnance_Survey_1st_series_1:105...
A full set of high resolution OS map scans is being gradually uploaded to Wikimedia Commons and indexed by historic county. These are very large files, 10,000 pixels wide, so are both in TIFF and jpeg format to make reuse easier.
These are of 'specialized' interest, but I would think could be of use to both Wiki Loves Monuments projects and readers of this email list interested in early maps and geo-related experiments. The maps show plenty of fine detail, including inns/pubs, churches, bridges etc. Those that still exist will be likely to be listed and protected, and those that are not, may still be great photography subjects. Note that to view the maps, Commons' in-built ZoomViewer is useful but it appears to be broken today, so you may have to settle for examining the full size jpeg in-browser.
As I write this, the uploads are working through "B", so the projects is going to take several weeks to complete. If there are ideas for how better to categorize or template these maps, feel free to drop a note on my Commons talk page. It is always possible to do some post-upload housekeeping or adjusting the way the uploads are currently getting formatted.
Thanks, Fae