The Info on some is not complete as you can see, please email me if you could fill in some gaps for me.  Most info comes from The Shadow Chronicles by Anthony Tollin
Comrade81@hotmail.com

The Shadow radio performers
James LaCurto: July 31, 1930-???
Frank Readick: ???-March 27, 1935
Orson Welles: September 26,1937-???
Bill Johnston: September 25,1938-March 21,1943
Bret Morrison: September 26,1943-April 16,1944 ; September 09,1945-December 26,1954
John Archer: September 24,1944-April 08,1945
Steve Courtleigh: fall of '45-???(left after only half a dozen episodes)

The Margo radio performers
Agnes Moorehead: September 26,1937-March 20,1938; September 25,1938-fall of '39
Margot Stevenson: Summer of '38
Majorie Anderson: fall of '39-April 16,1944 (died the same year)-
Judith Allen: September 24,1944-April 08,1945
Laura Mae Carpenter:?????(performed along side Courtleigh)
Lesley Woods: September 09,1945-May 26,1946
Grace Matthews: September 08,1946-June 05,1949
Gertrude Warner: September 11,1949-December 26,1954

Walter B. Gibson (Maxwell Grant)
Writer and creator of The Shadow Magazine and influenced the movies and radio of the same.

Shadow Movies and Serials:
The Shadow Strikes(1937)
The Shadow(1940)
Behind the Mask(1946)
The Missing Lady(1946)
The Shadow Returns(1946)
The Invisible Avenger(1958)
The Shadow(1994)

Actors on the silver screen to portray The Shadow
Victor Jory
Rod La Rocque
Alec Baldwin

Little known facts:
 The man who suggested the idea to call the phantom avenger The Shadow (Harry Charlot) was found poisoned in a Bowery flophouse that he had entered under an assumed name.  His murder remains unsolved to this day.

 James LaCurto was the first actor to portray The Shadow
 
 Walter B. Gibson was a magician before becoming a journalist and writer.

 Gibson wrote and amazing 283 shadow novels totaling over 15 million words over 2 decades.

 In the novel "The Shadow Unmasks" The Shadow was revealed as Kent Allard, an internationally famous aviator supposedly "lost amidst a tribe of Xinca Indians in the Yucatan Peninsula at the very time when an amazing personage known as The Shadow first begun to harass America's unwanted gangland.

 Gibson did all his Shadow novels on a first draft basis.

 Shadow actors Orson Welles(The Shadow), Agnes Moorehead(Margo Lane), Ray Collins(Commissioner Weston), Paul Stewart and Everett Sloane all were in the movie Citizen Cane.

 Shadow actors Orson Welles(The Shadow) Frank Readick(The Shadow) Ray Collins(Commissioner Weston) Carl Frank and Kenny Delmar put together the Mercury Theatre production of "War of the Worlds."

 Blue Coal sponsored The Shadow for almost two decades