The first prominent baseball cards, called Old Judge, were first issued in 1887.
Notes on verification
Corroborated by PSA CardFacts and Library of Congress, both authoritative sources on the topic. Minor variation in some secondary sources (1886 start) does not undermine the predominant, well-supported 1887 date. [tier=silver indep_score=0.925 clusters=2 claim_tier=notable]
Sources
- Would Baseball have Become America's National Pastime Without ... (seed:culture_and_philosophy)
- https://www.psacard.com/cardfacts/baseball-cards/1887-old-judge-n172/111 (corroboration)
- https://www.loc.gov/collections/baseball-cards/articles-and-essays/baseball-cards-1887-1914-card-sets-in-chronological-order/ (corroboration)