On the 16th of September 1620, the Mayflower sailed from Plymouth, England, for New England. They spotted Cape Cod on the 9th of November 1620. The pilgrims had intended to head south to the Hudson River, New York, to settle, but the weather was so bad, they decided to stay at Cape Cod and explore the area.
There are planned joint celebrations in the UK, America, and the Netherlands, as many English pilgrims were living in exile there. The UK website is mayflower400UK.org, there are a few US sites, themayflowersociety.org, boston.com, plymouth400inc.org.
I am certainly looking forward to the events next year