I was surprised to learn that architecture was covered by copyright. I hadn't really looked at copyright law in depth since the 80s other than some organization

I was surprised to learn that architecture was covered by copyright. I hadn't really looked at copyright law in depth since the 80s other than some organization around trying to get IP protection for type design in the 90s which never got anywhere. I remembered reading that architectural plans were specifically excluded from copyright protection but apparently in 1990 this changed. (Note that all of this applies specifically to US copyright law.)