Coadjutor bishop
In 1816 he was nominated Bishop of Philadelphia, but at his request the nomination was withdrawn and, on July 24, 1817, he was appointed Coadjutor bishop to Archbishop Leonard Neale of Baltimore, and Titular of Stauropolis. The brief of the appointment had not reached Baltimore when Archbishop Neale died, and Maréchal was not consecrated Archbishop of Baltimore by Bishop Cheverus of Boston until December 14, 1817.