That's close to the latitude of the Antarctic Circle.
The Arctic Circle is located at approximately 66.5 degrees latitude north. This corresponds to 66 degrees and 30 minutes north.
You're talking about the 'Arctic Circle'.
The island possession located at approximately 18 degrees N latitude and 66 degrees W longitude is Puerto Rico.
Finland
The imaginary line located at 66.5 degrees south latitude is called the Antarctic Circle. This is the southernmost latitude at which the sun can remain continuously above or below the horizon for 24 hours during the summer and winter solstices, respectively. It marks the boundary of the Antarctic region.