When I view this in Chrome, http://localhost:90 the file is downloaded instead of displayed in Chrome.

This question has been asked a lot of times on SO, but about index.php files. My problem is a plain jane HTML file, not a PHP file. That hasn't been asked yet. I was hoping the solution would be similar, but I haven't been able to figure it out.

Here's my example.com.conf:

server
{
    server_name localhost;
    listen 90;
    root /var/www/example.com/html
    index index.html

    location / {
        try_file $uri $uri/ =404;
    }
}

My index.html file contains only two words, no markup

Hello World

I think it's the mime.types. The mime.types file has the entry for html in it. This is a fresh nginx install.

nginx -t reports "test is successful"