== Possible math or quotation error == 

 This statement appears twice in the article, once in the intro and once in the section Phases: 

 "Chetro Ketl required an estimated 50 million sandstone blocks and more than 500,000 man-hours to complete." 

 At this rate, the masons were quarying, transporting, shaping, and laying 100 sandstone blocks per hour, to say nothing of mixing all that mortar.  Obviously, something is wrong here. 

 The line refers us to Citation 54, which in turn references two different sources: 

 Metcalf 2003, p. 77: 500,000 man-hours; Fagan 2005, p. 9: 50 million sandstone blocks. 

 Apparently these workers used different methods of estimating, or were estimating different parts of the whole, or something.  Whatever the case, these numbers shouldn't simply be tossed into the article with a comment on the discrepancy. 

   Martin Meiss