- "'[Minerva McGonagall] sent an owl to Hogwarts, asking whether she might be considered for a teaching post. The owl returned within hours, offering her a job in the Transfiguration department, under Head of Department, Albus Dumbledore."
The Transfiguration department is a department at Hogwarts School of Witchcraft and Wizardry, made up of professors who teach Transfiguration. The Head of Department was Albus Dumbledore during the 1950s. By 1956, there was a vacancy in the department, so Dumbledore gave Minerva McGonagall, who had applied for a job at the school, the position.  After Professor Dumbledore became Headmaster, following the departure of Armando Dippet, Professor McGonagall became Head of Department.