all list pages are broken

[elements-ix]

Hugo 0.58.3
Go 1.13

My content directory looks like this:

content/
  posts /
    foo.md
    bar.md
  about.md

My site will render the about.md page just fine, but nothing shows up in the post list on localhost:1313/posts/, and if I try navigating directly to a post like localhost:1313/posts/foo/ I get a 404. Am I doing something wrong?