 Cummings, asked Archbishop Hughes to appoint McGlynn as his assistant.At the death of Cummings, the following year, McGlynn became pastor, at the age of twenty-nine, of St. Stephen's Church on East Twenty-eighth Street, one of the largest parishes in New York, where he served as pastor until 1887.During this time, Constantino Brumidi, who painted The Apotheosis of Washington on the dome of the Capitol building in Washington, painted a fresco of the Crucifixion in St. Stephen's Church, for which he also executed a "Martyrdom of St. Stephen" and an "Assumption of Mary".