Craft not generating language links correctly {{siteUrl}}, {{category.url}}, {{product.url}}, etc. is not outputting any language.

The main language is Norwegian. I created a folder for English (/en/) with define('CRAFT_LOCALE', 'en_us');

Navigating to site.com/en works fine, and all the english content shows as expected. However any link generated by craft simply omits "/en/", thus throwing me back to Norwegian. I don't get it.

Anything in particular I should look into? Thanks a lot!
In a multilingual site, your siteUrl config setting in /craft/config/general.php needs to be an array where the keys correspond to your installed locales:

return array(
    // ...
    'siteUrl' =&gt; array(
        'no' =&gt; 'http://example.com/',
        'en_us' =&gt; 'http://example.com/en/',
    ),
);