Hello Hope
I have found your Snow family on the following Census:
1851 : Parsonage Place, Oldbury, Staffs
Samuel Snow, Head, 30, Coal Miner, Born Donington, Salop
Elizabeth Snow, Wife, 25<
Sarah A Snow, Daur, 2, Born West Bromwich
William Snow, Son, 1 Month
Others Born in Oldbury, Worcs
1861 : Tat Bank Road, Oldbury, Staffs
Samuel Snow, Head, 42, Coal Miner, Born Donington Wood, Salop
Elizabeth Snow, Wife, 36
Sarah A Snow, Daur, 12, Scholar, Born West Bromwich
William Snow, Son, 10, Scholar
Ellen Snow, Daur, 7, Scholar<
Henrietta Snow, Daur, 4, Scholar
Benjamin Snow, Son, 1
Others Born in Oldbury, Worcs
1871 : Rood End, Oldbury, Staffs
Elizabeth Snow, Wife, 44, Wid, Charwoman
Sarah A Snow, Daur, 23, Glass Smoother, Born West Bromwich
William Snow, Son, 21, Sheet Glass Cutter
Hepzibah Snow, Daur, 14, Screwing
Benjamin Snow, Son, 12
Elizabeth Snow, Daur, 9
Henry Snow, Son, 5<br>
Sarah Hadley, GrMother, 70
Others Born in Oldbury, Worcs
From these Census Records, their first daughter Sarah was born around 1849 in West Bromwich, so it's probably that Samuel and Mary married in or around West Bromwich.
See if you can find their marriage on FreeBMD
Maggie