Many Meachams
The Character of corrupt Indian Agent Silas Meacham comes from history.
Fort Apache is loosely based on the short story "Massacre" by James Warner Bellah. Though it is a reinterpretation of Custer's Last Stand in 1876 it is set during the Ute War (in 1879 in real history) and so could be considered a combination of The Little Big Horn and Major Thornburgh's defeat.
Bellah's novel "White invader" or Rear Guard, filmed as The Command(1954), involved a unit riding to reinforce the army of General Crook after Custer's Last Stand in 1876. I believe I remember reading the Doctor thinking that he remembered the Thursday Massacre. Thus in this fiction series by Bellah Thursday's Disaster happened in or before 1876 despite being based on events in 1876 and 1879.
This timeline puts "white Invader" in 1876 and "Massacre" in 1874. http://www.personal.utulsa.edu/~marc-carlson/misc/Bellahtime.htm
As I remember, the story "Massacre" included the White River Indian agent Custis Meacham taking the place of Nathan C. Meeker, the historical agent at White River in 1879 (honest but tactless in his dealing with the Utes), so Meacham's character comes from the original story. And Meacham's name is another historical ingredient in Bellah's mixture, a name I recognized from the Modoc War of 1873.
And as this http://en.wikipedia.org/wiki/Alfred_B._Meacham shows Alfred B, Meacham (1826-1182) was about the opposite of Silas Meacham, a supporter of Indians rights instead of a greedy exploiter of them.
So the character of Meacham had a long evolution from his historical roots, both good men, to the "blackguard, liar, hypocrite and stench in the nostrils of honest men" seen in Fort Apache.
One of the disappointments of Fort Apache is that we see Silas Meacham beside Thursday the day before the battle but do not recognize him among those killed the next day, though he deserves it more than anyone else.