Hey Folks,
Wget is indeed a great utility. It can download a website (or a partial one) and can even relink the HTML to operate properly locally.
As Vince noted it’s not available by default on macOS. You have to install it via MacPorts, Homebrew, or make it yourself from source.
Wget will NOT create a webarchive file though. For that you need something more specific.
In addition to the other methods described above there’s an Unix executable called webarchiver.
It’s several years old, but I just tested it successfully on macOS 10.12.4.
It’s also available through MacPorts.
Usage is very simple:
webarchiver -url <URL> -output <POSIX Path to new file name>
-Chris