Lee de Forest was born in 1873 in Council Bluffs, Iowa, the son of Anna Margaret (nee Robbins) and Henry Swift DeForest. He was a direct descendant of Jesse de Forest, the leader of a group of Walloon Huguenots who fled Europe in the 17th Century due to religious persecution. De Forest's father was a Congregational Church minister who hoped his son would also become a pastor. In 1879 the elder de Forest became president of the American Missionary Association's Talladega College in Talladega, Alabama, a school "open to all of either sex, without regard to sect, race, or color", and which educated primarily African-Americans.

At the 1904 Louisiana Purchase Exposition, Valdemar Poulsen had presented a paper on an arc transmitter, which unlike the discontinuous pulses produced by spark transmitters, created steady "continuous wave" signals that could be used for amplitude modulated (AM) audio transmissions. Although Poulsen had patented his invention, de Forest claimed to have come up with a variation that allowed him to avoid infringing on Poulsen's work. Using his "sparkless" arc transmitter, de Forest first transmitted audio across a lab room on December 31, 1906, and by February was making experimental transmissions, including music produced by Thaddeus Cahill's telharmonium, that were heard throughout the city.  On July 18, 1907, de Forest made the first ship-to-shore transmissions by radiotelephone -- race reports for the Annual Inter-Lakes Yachting Association (I-LYA) Regatta held on Lake Erie -- which were sent from the steam yacht Thelma to his assistant, Frank E. Butler, located in the Fox's Dock Pavilion on South Bass Island. De Forest also interested the U.S. Navy in his radiotelephone, which placed a rush order to have 26 arc sets installed for its Great White Fleet around-the-world voyage that began in late 1907. However, at the conclusion of the circumnavigation the sets were declared to be too unreliable to meet the Navy's needs and removed.  The company set up a network of radiotelephone stations along the Atlantic coast and the Great Lakes, for coastal ship navigation. However, the installations proved unprofitable, and by 1911 the parent company and its subsidiaries were on the brink of bankruptcy.Answer this question using a quote from the following article:

When did Lee de Forest work on Arc radiotelephone development ?
On July 18, 1907, de Forest made the first ship-to-shore transmissions by radiotelephone