Margaret McBride b. 1815 Ireland d. 8 May 1865 Jefferson Co., New York
do you know for certain that is the right one ?
Ireland, Select Births and Baptisms, 1620-1911
Thomas William Baily
Baptism Date 4 Jan 1813
Baptism Place Ballyhay, Cork, Ireland
Father John Baily
FHL Film Number 962669
and it is baptised - not born - he could have been born a few months earlier.
do you have proof that they were married 5 Aug 1840 Alleghany, Pennsylvania ?
Assuming this is the right family [looks like it]:
From near Pittsburgh to Theresa/Alexandria/Redwood, Jefferson County, New York, where they were 1850 to at least 1942, is over 400 miles.
And the question is: why move then ?
Plus: all the children were born in NY, including Mariann, Elisabeth & Mary Jane: about 1837 to 1840
You could be right, but this does not look too logical.
[that family is easily found to at least 1942 in the vicinity of Theresa, example: 1942: George Piper, son of Mary Jane Bailey]