I don't know whether this will help, but here's the owner's obituary:

Palm Beach Post, The (FL) - Monday, October 24, 1994
BRUCE M. LEWIS
Age 88, of Lost Tree Village, North Palm Beach, Florida died Thursday, Oct. 20, in the Manors at Hobe Sound. He was the former President and CEO of the Lewis Historical Publishing Co., The American Historical Publishing Co., and Who's Who Inc. of West Palm Beach, Fla. He was a Director of the Atlantic National Bank, and former Mayor of Palm Beach Shores. He was born in Brooklyn, New York the son of Marian L. and Mabel E. Lewis. He graduated from Dartmouth College and resided in Nutley, NJ until he decided to relocate his business from New York City to West Palm Beach in 1960.
He is survived by his wife, Thelma; a son, Ralph E. Lewis of Macungie PA; a daughter, Mary Virginia Cypher of Butler PA; 13 grandchildren and 24 great grandchildren.
Funeral Services will be held at the WM. N. HOWARD FUNERAL HOME, 754 U.S. Hwy 1, North Palm Beach at 2 pm on Wednesday, Oct. 26. Those planning an expression of sympathy are asked to consider memorial contributions to the Oceanview United Methodist Church, 701 Ocean Dr., Juno Beach FL 33408.

So in 1960 American Historical Publishing was based in West Palm Beach. Florida corporation records might have something...