I've written before about how King Charles II granted Connecticut a Royal Charter in 1662. The Charter allowed Connecticut a high degree of self-government - something Connecticut residents got used to enjoying!
After Charles' death in 1685, his brother, James, became King. James sought greater control over the American colonies and decided to create the Dominion of New England by combining the New England colonies of Connecticut, Massachusetts, New Hampshire and Rhode Island into one large colony. He appointed Sir Edmund Andros as the Governor of the new colony.
Those in Connecticut attempted to defy/resist the new arrangement by refusing to turn over the colony's Royal Charter and insisting it was still in effect. In a move more symbolic than literal, Andros, accompanied by British troops, went to Hartford, Connecticut to meet with local leaders/representatives and to retrieve Connecticut's Royal Charter.
As legend has it, during a meeting at Sanford's Tavern (in Hartford) between the Connecticut delegation and Andros, the meeting was suddenly plunged into darkness (the room's candles were extinguished) and confusion ensued. During this time, it is said that the Charter that was present was taken by Joseph Wadsworth and hidden in the hollow of a large oak tree on Samuel Wyllys' property for safekeeping.
The Charter is said to have been kept in the tree from 1687 to 1689, until such time as King James II was removed from the throne as part of England's "Glorious Revolution" and Andros was no longer in power. (I wonder how well a piece of parchment would "weather" exposed to the New England elements for two years?)
Today, its unclear how much of the "Charter Oak" story is exaggerated legend - for effect - and how much - if any - of it is true. (There isn't much verifiable proof of the events described.) In any case, the story has been a rallying cry for Connecticut (and American) patriots for more than 300 years! Its story of resistance against the British is a ubiquitous part of Connecticut's history!
Note 1: The famous "Charter Oak" was felled by a storm in 1856; a memorial marker was erected at its location.Note 2: Even though Andros returned to England without Connecticut's Charter, it did not mean King James II did not move ahead with his "Dominion" plan or that Andros did not assume local authority over Connecticut and its neighboring colonies - both verifiably happened.Note 3: Some believe that the Charter present at the meeting with Andros was a copy of the original vs. the actual Charter.Factual or not, it was only natural that the famous tree (and by extension, its story) was selected for inclusion on Connecticut's 1935 commemorative half dollar.
1935 Connecticut Tercentenary Half Dollar

The tree also appears on Connecticut's 1999 State Quarter:
1999 Connecticut State Quarter
(Image Credit: US Mint media images. Fair use, education.) For other of my posts about commemorative coins and medals, including other Connecticut Tercentenary stories, see:
Commems Collection.