First child of William and Ann registered in Knaresborough (Margaret) and this appears to be where the couple married too:
William Allan
Ann Watson
June quarter 1861 Knaresborough - Vol. 9a, Page 129 (2 of the 4 people sharing that page reference)
To confirm (copy of marriage certificate on FindMyPast):
William Allan 20, son of Peter, and Ann Watson 18, dau. of James (residence for both shown as Darley) married 22/4/1861 Hampsthwaite, Yorkshire.
Annette