Just above 15 mhz was a fairly popular pirate frequency maybe 20 or 25 years ago. The only time I ever heard a pirate when I lived in the SF Bay area, around 1990 or so, was on 15.015 or 15.025 mhz (I can't remember which), and this was during the afternoon on the Left Coast.
Quite a few Europirates use 15 MHz for transmissions to the US, usually between late mornings and early evenings our local time. When solar activity is fairly high, it's a great band (similar to 20 meters for ham radio, which is considered the "dx band"), although obviously it hasn't been so great this solar max.
Likewise, 11 meters can also get out with fairly low power when conditions are good. I use the STLs (studio transmitter links) on 25910, 25950, and 25990 as beacons to tell how 11 meters is doing, if I want to try to listen to freebanders. 25950 is from Colorado, the other two from Texas. They use FM, btw, not AM. I believe they run a few hundred watts.
Several pirates in the past have transmitted on SWBC frequencies, going on just when the SWBC station goes off the air, hoping to be heard by a few listeners of the SWBC station. It's an interesting approach.