Columbus Day postal woes

I wanted to send a New York postcard to my old host family back in Cusco, Peru, before I left for Boston. So this morning, I went to the Central Post Office, near Penn Station in Manhattan, to send off the postcard. Well, it turns out that going to the post office on Columbus Day is a Really Bad Idea™. The Central Post Office was, apparently, the only post office in all of Greater New York that was open today. I walked inside, and there was one service desk open (with the other 25 or so roller-doored shut), and nobody at the information booth, and a queue that was literally about 100 feet long (that's over 30 metres!). And all I wanted to do was buy a stamp. Stuff that — I'm not waiting 3 hours to buy a daym stamp — I'll send the bloody thing in Boston.