No birthplaces shown in reply re 1861 above
1861 shows all older children were b Ireland as were parents Francis & Ann. John aged 20 is the first b England. Birth reg is on freebmd & GRO online shows mmn Purdom but Mary’s birth has mmn Urwin
A quick look at the later census returns shows John Gallon consistently says he was born c 1840 at Felling Shore.
That birth reg with mmn Purdom was in Q2 1842, so a little late plus it was registered in Durham & Lanchester which doesn't cover FellingShore.
https://www.ukbmd.org.uk/reg/districts/durham.htmlI can't see a likely birth registration for him in Gateshead District (or anywhere else) but I did find a possible baptism and from there I think the following may be possible - though the confirmation would be what name and occupation of his father on the 1862 marriage certificate to Sarah Jane Robson. The census returns are transcripts only on FS, but the info will allow you to find them and get the images if you, or your library, have access to FindMyPast or Ancestry. I'd advise always looking at the images if possible as transcripts may be inaccurate.
NB this is just 'possible', you'd need to check it out carefully. I'm as capable of taking a wrong turn as anyone :-)
1833 marriage Edward Gallon and Esther Urwin - BTs Gateshead Fell 1833
https://www.familysearch.org/ark:/61903/3:1:S3HT-67T9-V3K?1835 Baptism of daughter Ann - BTs St Mary Heworth
https://www.familysearch.org/ark:/61903/3:1:S3HY-DHW9-6C4?1837 Baptism of son Simon - BTs St Mary Heworth
https://www.familysearch.org/ark:/61903/3:1:S3HY-DHW9-X3D?1838 Baptism of son Thomas - BTs St Mary Gateshead
https://www.familysearch.org/ark:/61903/3:1:S3HT-69CS-7Q2?GRO Births 1838 Q3 Gateshead Union 24 107 mmn IRWIN
1
840 14th May Baptism of son John - BTs St Mary Heworth
https://www.familysearch.org/ark:/61903/3:1:S3HY-DHW9-6C2?and oddly another baptism record for him 3 months later in Gateshead!
1840 14th August Baptism of son John - BTs St Mary Gateshead
https://www.familysearch.org/ark:/61903/3:1:S3HT-69CS-7Q2?1841 censushttps://www.familysearch.org/ark:/61903/1:1:MQBZ-3MP?lang=en1844 Baptism of daughter Mary - BTs St Mary Heworth
https://www.familysearch.org/ark:/61903/3:1:S3HY-DHW9-XDW?GRO Births Q2 1844 Gateshead Union 24 153 mmn URWIN
1851 censushttps://www.familysearch.org/ark:/61903/1:1:SGV3-426?1861 censushttps://www.familysearch.org/ark:/61903/1:1:M7X2-VRD?lang=enBoo