English cartographer and engraver. He was one of the most prominent and prolific map compliers and engravers of his day. Our first records of Jefferys appear in the 1735 when he was apprenticed to Emmual Bowen. Later, in the 1740s he is known to have engraved several maps of the popular "Gentlemans' Magazine". Around 1740 Jefferys was finally able to go into business for himself and in 1746 was appointed "Geographer to Fredrick, Prince of Wales", which shortly after translated to the position of "Royal Cartographer to King George the III". While not specifically a cartographer, Jefferys specialized in compiling and re-engraving the works of various cartographers into coherent cartographic wholes. While not salaried position, Jefferys appointment as "Royal Cartographer" did give him preferential treatment as well as access to the most up to date cartographic material available.
He his best known for his maps of the America, particularly The American Atlas, which included some of the finest and most important maps of America ever published. His American Atlas is the most important 18th-century atlas for America, described by Walter Ristow as a "geographical description of the whole continent of America, as portrayed in the best available maps in the latter half of the eighteenth century... as a major cartographic reference work it was, very likely, consulted by American, English, and French civilian administrators and military officers during the Revolution."
Despite his prolific publishing history, royal appointments, and international publishing fame, Jefferys lived most of his life in dire economic straits. It is recorded that he had to be bailed out of bankruptcy by the Sayer firm during the publication of The American Atlas and in the end, he died with very little. Nonetheless, his cartographic legacy remained and, even after his death in 1771, many of his important maps continued to be published and republished by the Sayer and Bennet firm. Jefferys was succeeded by his son, also Thomas, who had little success and partnered with Faden.