That's Ken Anderson (1909-1993). In a 2003 article, Disney historian Jim Korkis (aka "Wade Sampson") suggested that when it comes to an appreciation of the talents who created the Haunted Mansion, Ken Anderson has been the "forgotten man." In some sense this stills feels true, even though objectively speaking, it is not. Not only Sampson, but Bruce Gordon and David Mumford (pp. 260-63 of The Nickel Tour), Leon J. Janzen (The "E" Ticket #13; Summer 1992), Ed Squair (The "E" Ticket #41; Fall, 2004), Jason Surrell (pp. 15-19 of The Haunted Mansion: From the Magic Kingdom to the Movies), and Jeff Baham have all tried to give Mr. Anderson his proper due, and I'm probably missing some authors in that survey. That's a lot more attention than most of the HM Imagineers have been given, so why does Anderson still feel like the "forgotten man"?
The answer is simple: It's because he had been off the project for over ten years by the time the Mansion opened. All the other big names who worked on the attraction stayed on. They simply accumulated over the years, leading to the "too many cooks" situation that Marc Davis would later bemoan. Anderson was the first man given the haunted house assignment for Disneyland, and he worked closely with Walt himself on the "Ghost House" for two years (1957-58) before Walt removed him and added him to the small army working on Sleeping Beauty at the time. Rolly Crump and Yale Gracey took over the project in 1959. When Marc Davis, Claude Coats, X. Atencio, Blaine Gibson, and so many other great talents were added to the crew in the 60's, Crump and Gracey remained, so Ken Anderson was in fact the only major talent to get "fired" from the Haunted Mansion assignment, and consequently he has nothing to do directly with anything you find in the finished attraction. Since you can't point to anything and say, "Ken Anderson did that," it is all too easy for him to slip off the radar screen.
If you've been down this road before, you already know that Anderson came up with four different show scripts during the course of 1957, but the four are hard to keep separate since they were continually being revised and they exhibit considerable overlap. Not only that, but Anderson produced a great deal of concept art for his Ghost House, and there is plenty in those that has no counterpart in any of the four show scripts, so clearly those scripts do not represent anything like the full extent of Anderson's ideas. I don't think there's much point in rehearsing yet again the contents of the four scripts; interested readers can check out some of the sources listed earlier. I recommend the Sampson link in particular.
I've got a different idea. What's say we wander through the Mansion and take closer note of things that go back originally not to Marc or Claude or X. but to Ken? This has only been done in a haphazard, hit-and-miss manner up to this point, and besides, I've got some goodies you probably haven't seen before. By the time we're through, it should be apparent that Anderson deserves the title, "Father of the Haunted Mansion."
First stop is the exterior and an observation we (and others) have already made more than once. Suffice it to say, yet again, that Anderson's sketch of the Shipley-Leydecker house in Baltimore became . . . The Look.