The Johns Hopkins University (CSSE dept) data on nations and the individual US state websites (which all have dashboards updated typically daily).

This site: https://covidtracking.com/

is excellent for US state data and is usually updated multiple times per day (they also have a running history per state). I typically combine that with double checking state sites to see if there are any more recent updates available for the date I'm locking in (eg for a post like this).

And of course the population figures are then used for each location to arrive at the per 100,000 number (the per 100k mortality data isn't provided like this anywhere else that I have found).