Article 6, Clause 2
Document 39
Gibbons v. Ogden
9 Wheat. 1 1824(See 1.8.3 [commerce], no. 16 )
The Founders' Constitution
Volume 4, Article 6, Clause 2, Document 39
http://press-pubs.uchicago.edu/founders/documents/a6_2s39.html
The University of Chicago Press