Nice work! A few tweaks below we can do to make it even better:
Need to close (and open) separate paragraphs here to get the right spacing between them.
The last item here should be part of the same, first-level list, not a new list.
Let's add the usa-class link to all links in the content area. (Otherwise, by default, there is no hover or focus state.)
For the secondary nav, instead of dead links, we can actually make these functional since they are just jump links. For the href, add "#credit" for example. Then add an id parameter to the actual heading to match, but without the hashtag. (id="credit")