Notes:
The marriage records for Allegany County, MD list the following entries.
8 Apr 1903 David Muma and Betsy Rice
13 Feb 1809 Robert Muma [Mumow] and Betsy Davis
9 Aug 1814 Jacob Mumma and Catherine Rice
22 Aug 1816 John Mumma and Polly Hoblitzel
1800 Census, MD, Allegany Co., Cumberland Town
Conrad Muma
males under 10 = 3 <=== Jacob, John & William
males 16-26 = 1 <==== Possibly a brother
males 26-45 = 1 <=== Conrad
females < 10 = 2 <===
females 10-16 = 1 <=== possibly a brother's wife or a sister
females 26-45 = 1 <=== Barbara
1810 Census, MD Allegany Co., Cumberland
John Muma
males under 10 = 2
males 16-26 = 1 (John)
females 10-16 = 1 <==== ??? possibly a sister of John or his wife
females 16-26 = 1 (wife)
1820 Census, MD, Allegany Co., Town of Cumberland
John Muma (Murna)
males 16-26 = 1
males 26-45 = 1 (John)
females 10-16 = 1 <==== ??? possibly a sister of John or his wife
females 16-26 = 1 (Polly Hoblitzel ?)
John is listed in his father's 1792 deed
John is listed as less than 10 in the 1800 census of his father 1790-1800
John is listed between 16-26 in the 1810, with children. 1784-1794
John is listed between 26-45 in the 1820 census with a son & wife. 1775-1794
He is deceased in his Father's estate documents recorded in 1837
Based on all of this, John has a birth range of 1790-1792
The marriage of John Mumma to Polly Hoblitzel in 1916 must have been a second marriage considering the ages of his children in the 1810 census
His death year of before 1837 since his "heirs of Cumberland County, MD" are mentioned. This strongly suggests he died in Cumberland County. It is likely that he died prior to 1820 as did his brother. His wife is not identified in the 1820 census so she was likely living with her parents or relatives.