Isaiah William Penn Lewis was an American lighthouse designer, builder, and engineer.
He was a nephew of Winslow Lewis, and was often critical of his uncle's work.
I.W.P. Lewis traveled to Europe to study European lighthouse design, and incorporated the lessons he learned into his work. He built a handful of pile lighthouses, most of which were in the Florida Keys.
In 1843 he made a report to Congress on the lighthouses in the country.