These are not commercial maps from Garmin, but instead free maps (unlocked!), made from public available data. For more details, check the link above. The maps are NOT in NT format, so also usable for older Garmin devices.

I'v checked the Washington map: works well with Mapsource 6.13.7 and 6.15.11
Problem: most hiking trails are missing - don't forget to load the Garmin trail maps as well.