[Quoth]

Why wouldn't they be? If you mean the main project, not the Australia and Canadian sites.

Edit:
USA Magazines got the author's copyright and then if the magazine didn't renew, the work became PD (in the USA). So not all Gutenberg USA content is actually author's life +70, which is the Mobileread rule.

it's complicated. Complain to Disney and USA Government.

Edit 2:
Then there are works that are publishing house names. No point in looking up death of Laura Hope, Franklin Dixon, Caroline Keen and others. Some will be PD and some not. Those people never existed. Some of the best Caroline Keen were by Mildred Birt.