Perhaps the most important event of Tyler's administration was the signing of the Treaty of 1842 with Great Britain. Ever since the Treaty of Peace of 1783, there had been a dispute over the northeastern boundary of Maine. If the boundary had been run according to the plain meaning of the Treaty of Peace, the people of Upper Canada would have found it almost impossible to reach New Brunswick or Nova Scotia in winter. At that time of the year the St. Lawrence is frozen over, and the true northern boundary of Maine ran so near to the St. Lawrence that it was difficult to build a road which would be wholly in British territory. So the British had tried in every way to avoid settling the matter. It was now arranged that the United States should have a little piece of Canada north of Vermont and New York and should give up the extreme northeastern corner of Maine. It was also agreed that criminals escaping from one country to the other should be returned. A still further agreement was made for checking the slave trade from the coast of western Africa.

Benjamin Franklin and Joseph Henry made great discoveries in electricity. But Samuel F. B. Morse was the first to use electricity in a practical way. Morse found out that if a man at one end of a line of wire pressed down a key, electricity could be made at the same moment to press down another key at the other end of the line of wire.