Lapthorne immediately surrendered his serve and the USA pair were back in the driving seat, but the Brits proved determined and broke Wagner's serve for 4-4.
Norfolk, Taylor and Lapthorne all held, leaving Wagner to serve to take the second set into a tie-break. The British pair dug deep and Norfolk clinched the second set with a backhand volley.
Norfolk then held serve convincingly to get the British pair off to a good start in the decider but Taylor held comfortably for 1-1.
Lapthorne was then broken as the USA duo edged ahead. The Britons forged two break points on the Wagner serve before the American came up with an ace on the first of them but then double faulted to tie the scores at 2-2.
Norfolk then lost his serve and the USA pair led 3-2 with a break. When Taylor held for 4-2 the match was slipping away from the British duo.
Lapthorne then surrendered his serve with a double fault, leaving Wagner to see out the match to claim gold.
Earlier, Israeli duo Noam Gershony and Shraga Weinberg had taken bronze with a 6-3 6-1 victory over Japanese duo Shota Kawano and Mitsuteru Moroishi.
In other action, the winning streak of Netherlands ace Esther Vergeer continues as she moved into the women's Singles final with a 6-0 6-3 triumph against compatriot Jiske Griffioen.
She will face another Dutchwoman in the medal decider, after Aniek Van Koot saw off Germany's Sabine Ellerbrock 7-5 6-2.
Medal favourites Shingo Kunieda and Stephane Houdet made it through to the semi-finals in the men's Singles before the Frenchman Houdet got one over on his rival when they met in the Doubles later in the afternoon, teaming up with Michael Jeremiasz to beat Kunieda and his partner Satoshi Saida.