Log of flash drives used on my Mac?

An old thread which may be helpful.

Is there a system log which displays which external media/storage devices were connected/disconnected from my system? If so, please advise me on how to do so.

Your past log viewing window continues to shrink at Apple's hands. Under a week now.

As of High Sierra 10.13.6 (17G65), it appears that Apple now retains the current day's system.log, and yesterday's as system.log.0.gz. This is likely a significant decrease in log retention since the 2015 article that dialabrain linked too.

Traditionally, UNIX machines have only kept system logs for up to 7 days, before purging the oldest log, and then rotating the log names in a daily cyclical housekeeping process. These took the format: system.log, system.log.0.gz, system.log.n.gz.

Along came Apple, and wrote their own ASL (Apple System Log) facility and began writing proprietary binary system logs into /var/log/asl. Right now, mine on High Sierra 10.13.6 shows asl files from Aug 31 thru Sep 2 (ongoing). Apple appears to have deprecated the above rotational system.log — maintaining now just a day old system.log.0.gz file. Both of these logging conventions can be viewed in the Console application.

Older system/asl logs could be restored from Time Machine if you really wanted to do that, provided you did not overwrite any of the system.log* files.

You're welcome. Not that I know of.