William H. Donahue practiced law in Minneapolis from 1881 to January 6, 1909, when he was appointed to the Hennepin County District Court by Governor John Johnson. He took the oath of office on February 1, 1909, and set to work. But he suffered from cancer, and took a leave of absence in mid-April to get treatment in Philadelphia. There he died on May 2, 1909, at age fifty-one. In memorial proceedings in district court later that month, Henry G. Hicks paid tribute to Judge Donahue on behalf of the county bar association:
"He was more than a good lawyer. He was a good man, who loved justice and hated injustice. He had an intense sympathetic nature. No one in distress ever applied to him without receiving help and encouragement. His best efforts at the bar were made for those who needed help, and who could make little or no return therefor.
"He was a true and loyal friend, who never tired in his efforts to serve those whom he called his friends. This quality was so marked in him that it sometimes stood in the way of his own advancement.
"Had he been spared, he would have made an excellent judge. His judgment of human nature was keen and accurate. His motives were of the best. His sense of right and wrong was so delicately attuned that no technical legal objection would ever have served as an excuse with him for doing an injustice."