Doc Savage was originally a property of the Street & Smith company.  Henry Ralston originated the idea and worked with editor John Nanovic who wrote a short story titled “Doc Savage, Supreme Adventurer.” Writer Lester Dent was hired to write the first Doc Savage story, “The Man of Bronze.”  Dent went on the write the bulk of the series.  

A steady flow of Doc Savage stories written by Kenneth Robeson flowed from the Street & Smith offices until the late 1940’s when the demand started to dry up.  By the end of 1949 the demand for pulp stories was ending.  Doc Savage ceased publication in that year with a total of 181 issues printed.

At the time Street & Smith ceased publication of its pulp titles, it also sold many properties to Popular Publications.  The hero pulp properties were retained by Street & Smith.

N. Y. PUBLISHER DROPPING ALL PULP MAGAZINES – Street & Smith announced it was ceasing publication of its last four pulp magazines and comics.  The company cited changes in public taste as the reason for the cancellation.  Source: Chicago Tribune, Sunday, April 10, 1949

Street & Smith continued its publication of style and fashion magazines for the next ten years.

In 1959, Conde Nast bought the Street & Smith properties.  Conde Nast is a company created by Conde Montrose Nast. 

Conde Nast Buys Street & Smith, Inc. –  It was announced that Conde Nast Publications bought the Street & Smith. 
Source: The Los Angeles Times, Wednesday, August 26, 1959

In 1964, Bantam Books began reprinting the Doc Savage stories in paperback under license from Conde Nast.  The series reprint was completed in late 1990. The reprinted series included one previously unpublished manuscript marking 182 stories for the set.

Sanctum Publications received a license to reprint the original Doc Savage series (1933-1949).  The first issue came out in 2006 and was completed in 2016.

Conde Nast is one of many companies owned by Advance Publications, Inc.  This is a private company founded by S. I. Newhouse, Sr.

All the Doc Savage stories are still under copyright in the United States.