Alexander Graham Bell is best known for the invention of the telephone on March 10, 1876. He made his first telephone call to his partner Thomas Watson. The invention came after Bell became interested in transmitting the human voice while working on transmitting telegraph messages across multiple frequencies.
After the invention, he took his new device to exhibitions and to Europe. He showed off his new invention to Dom Pedro, the emperor of Brazil, at the Centennial Exhibition in Philadelphia later that same year. On July 9, 1977, Bell started his own company, the Bell Telephone Company. The invention took off immediately, and over 150,000 American citizens owned a telephone by 1886.