Starting in the 1980s, the diamond industry began to promote Valentine's Day as occasion for the giving of fine jewelry. Chocolate and NECCO wafers have been around for well over a century, and E-Cards didn't become popular until the 1990s.
Shakespeare refers to Valentine's Day in Hamlet (Act 4, Scene 5) when Ophelia sings:
To-morrow is Saint Valentine's day,
All in the morning betime,
And I a maid at your window,
To be your Valentine.
Then up he rose, and donn'd his clothes,
And dupp'd the chamber-door;
Let in the maid, that out a maid
Never departed more.