Some advice for those considering a timed entry ticket for the Washington Monument, because it took me a couple tries to get it right:
Timed entry tickets go on sale at recreation.gov exactly 3 months in advance, and PRECISELY AT 10:00AM ET.
Not 10:01. Not 10:03. EXACTLY 10:00.
I learned the hard way that tickets for the summer tourist season can literally sell out in just 3-4 minutes... makes Disney ADR bookings look like child's play. Third time was the charm for me- frantically kept hitting refresh at 9:59 and then grabbed tickets the very second they went on sale.