I used Historypin, a crowd-sourced platform that allows individuals and institutions to post historic images and text overlaid on a Google map.  The site appears to be uncurated and could benefit from some editorial oversight.  Multiple “pins” appear for the same site in many cases; the same image might be repeated several times; caption texts range from simple identifications to the type of explanations you might see in a historical society or museum.  I also wished that you could “toggle” between the current street view and the historic image.  Once the historic image appeared, it obscured the underlying view, which I suppose would be OK if you were at the actual site but not as useful if you are exploring at home.  I didn’t have the chance to test this on my cellphone due to Covid, but I imagine due to spotty WiFi that it might be challenging to use on the fly, and I’m not sure how quickly it would load using a cellular connection.  The site didn’t seem to privilege any particular historical approach, although it’s open-access, crowd-sourced nature does encourage local individuals to participate (along with the comment feature that allows individuals to add additional information to a posted/pinned entry).  With a little more oversight and more active outreach to local historical societies this site could be much more useful.