He married Miss Mary Ann Kelly, of Adams township, Muskingum county. He began his ministerial work in Carrollton, Ohio, soon after his graduation. He remained there but a short time. He served in Donegal, Westmoreland county, Pennsylvania, from 1857 to April 1868, after which he became pastor of the Lutheran Church in Gilford, Medina county, Ohio. Here he labored until April 1874, when he accepted a call to Venango, Crawford county, Pennsylvania. He served here until 1880, when he retired from the active duties of the ministry. He bought a piece of ground opposite the campus of Theil College, Greenville, Pennsylvania, and built himself a comfortable home. Here he and his wife provided boarding for a few students of the college. Those who were fortunate enough to secure boarding at this place were envied, more or less, by the other students, because the Gaumer home had the reputation of being a choice boarding house. Two of the former pastors of this parish had the good fortune of boarding at this home. His attendance at the services of God's house in Holy Trinity Lutheran Church of Greenville was unfailing.

The following excerpt is taken from his obituary in the Lutheran:

"Rev. Gaumer was a godly man, kind and gentle in disposition, a faithful and methodical pastor, a sound theologian, and a most devoted Lutheran. He was beloved by all who knew him. In all the parishes he served, he has left memorials of his faithful and self-denying labor, and his memory is lovingly cherished by many friends. When the disabilities of age came upon him, he disposed of his property in Greenville, gave the proceeds to the Passavant Hospital, and he and his wife made their home there. Loving hands ministered to his wants and smoothed his pathway to the tomb. His last sickness was brief and painless. He gently and sweetly fell asleep. In accordance with his request, he was buried at Greenville."

He died May 7th, 1901, aged 81 years 2 months and 4 days.