My first memories of him come from watching the '57 Series with my Mom and grandfather. My Dad took me to Yankee Stadium almost weekly beginning in 1960 so I saw him play often.
And I can say with first-hand knowledge that there was an obsession with Mantle cards back then. I recall discussions in my North Jersey schoolyard about how Topps wasn't distributing Mantle cards in our neighborhood stores to encourage more pack buying.