I believe Drupal seems to be the official of CMS of Stanford.edu and many of its departments' sites [0]. And back in the day, Drupal's adoption by President Obama's first CTO was noteworthy [1]. I don't think Drupal made huge inroads in the rest of the federal government, but the White House Github page shows that they still use and maintain Drupal module and theme code: https://github.com/whitehouse

[0] https://drupalcamp.stanford.edu/

[1] https://www.drupal.org/node/613892