When did Bell get the American telephone patent?

Bell changed the tuning fork into a metal piece that can vibrate with the sound, and changed the iron core into a magnetic rod. After repeated experiments, he made a practical telephone device. 1876, Bell obtained the telephone patent in the United States. 1877, the first telephone line in Boston was opened. In the same year, the first news telegram sent by telephone was sent to Boston's Le Monde, which began the era of public telephone use, and Bell thus established his immortal position in the history of world science and technology.