These days, most people think of the Presidential Plane as the Boeing 747s currently serving in that role. Back in Johnson's day as president, Boeing 707s flew that mission. And, there's Marine One, the helicopters used to ferry the President on shorter flights. And, there are other aircraft used by the President as needed.
Johnson had used his ranch on the Pedernales as a base for years, and had a 3,000 foot grass strip for flying in and out during his years in Texas politics and later Congressional service. When he ascended to the Presidency following the assassination of Kennedy however, his transportation needs changed. As big as the ranch was, putting in a strip capable of handling a 707's size and weight was not really an option. But, there are a variety of aircraft at the President's disposal, and the Air Force VC-140 (Or C-140 in other roles) was put to the task - along with a paved 6,300 foot strip.
According to the National Park Service website,
President Johnson flew home to his Texas ranch 74 times during his 5 years in office, living and working for 490 days—or about one-fourth of his presidency—at the Texas White House...This placard from the National Park Service display shows the working set up that made this possible. The aircraft is parked in the picture just about where it's displayed today.
Note that it has 4 engines - that's partly a reflection of the reliability of the small jet engines of the day, and the amount of power they could put out. Two on each side of the tail is rather like the Vickers VC-10. McDonnell took a different approach with the Model 119 rival to the JetStar.
The cruciform tail had a feature that was notable as well. Putting the elevators halfway up the rudder got them out of the wash from the engines, but made adjusting them problematic. Lockheed solved the problem by putting the whole rudder-elevator assembly on a mount that moved the rudder up and down to change the angle of attack of the "all-flying" stabiliator. The joint can be seen as the unpainted silver arc along the base of the rudder in the picture of the tail.
Here's a couple more photos to close this out. Enjoy!