Each year, we celebrate December 1st as the day Iceland gained sovereignty from Denmark. The Act of Union was an agreement with Denmark, where Iceland was recognized as an independent country. Although this was not total independence as Iceland was still in a personal union with Denmark, it was a great achievement.
The video below is in English and is well done with photos, videos, and the story about Iceland's Sovereignty of 1918.
Natalie Guttormsson wrote an article a few years ago and you can read that article here:
A quote from the Morgunblaðið newspaper that day read:
“Today, we stand face to face with the world as Icelanders, not as Danes – on our own responsibility, not on others.”