Father Michael O'Donnell was by Father Ryan's bedside at the time of his death. His presence in Lockport, while related to Father Ryan's condition, was connected to another tragedy he was experiencing at the time. At Ottawa, Illinois, Father Thomas O'Donnell lay mortally ill. Older brother to Michael, Thomas was himself a pioneering priest. He was one of the first priests ordained by Bishop Quarter and sent to the parish at Ottawa, St. Columba, along the southernmost end of the Illinois and Michigan Canal. He died only twelve days after Father Ryan. Father Michael knelt at his side as he expired.

The earliest records of St. Dennis parish that are still intact are in the handwriting of Reverend Michael O'Donnell. The register of baptisms and marriages has an introduction in Latin dated beginning 1852. The baptismal section covers 1852 through 1857. The marriage section dates from 1852 through 1854. The first names are scribed in Latin with the surname in English.

Michael O'Donnell was a graduate of the University of St. Mary of the Lake. During the early part of his road to priesthood he assisted in the consecration of St. Mary's Cathedral in Chicago on October 5th, 1845. The following March 19th, the tonsure was conferred upon him. His ordination took place on the 10th of April 1852.

Father O'Donnell came back to Lockport as pastor on the 23rd of September 1852, with his first entry in the register appearing on the 30th. The missions from the outskirts of Joliet to Summit were under his care. Within the month, on the 19th of October, Father O'Donnell officiated with Bishop Van de Velde of Chicago in Confirmation of 96 people at the Sag (about four miles east of Lemont). He began building the old church of St. James at Sag but did not live to see its completion.

At one point in his ministry Father O'Donnell visited Galena and its out-missions, quite possibly on a fundraising mission. Early 19th century Galena was a very prosperous section of the country due to mining and commerce along the Mississippi River.

Father O'Donnell inaugurated the first celebration of St. Patrick's Day at St. Dennis in 1853. It was recorded in the diocesan paper of the day, 'The Western Tablet', that a "...large and respectable number met on this occasion."

The last log in the register made by Reverend Michael O'Donnell occurred on the 19th of July 1854. He died of cholera on July 31, 1854, at the very young age of 36.