As part of their social media efforts, a number of sites have posted games, puzzles, and other online activities based on their collections and historic structures/landscapes. To pull them all together (or as many as I could find) - Trailheads Rec Room. Sites have often posted more than one of any type of activity, so I'm embedding one of the most recent to let you know to look for more on their Facebook page.
Here's a multi-site activity highlighting Morse Code communication (and a Morse Code translation tool).
Note: on 8/14/2020, I added this State Museum of Pennsylvania post related to Morse Code.
Erie Maritime Museum & U.S. Brig Niagara (EMM Facebook page)
The State Museum of Pennsylvania (SMP Facebook page)