William Hughes Incorporated was a contracting business specializing in brickwork. The business was run by two German-born brothers, George J. and William Hughes. According to existing advertisements, their business was operating in 1923, and they were still taking projects in 1956. The company provided estimates for work in the Dumbarton Oaks Gardens, Washington, D.C.
References:
1920 United States Census (Population Schedule), Washington, Washington, District of Columbia; p. 9B, Line 61, Gregory Psalti household; digital images, Ancestry.com (http://ancestry.com, accessed August 18, 2014); citing NARA microfilm publication T625, roll 205.
"Advertisements for George J. and William Hughes, brick work, Gillis & Geoghegan, 'electric telescopic hoists,' National Mosaic Co., Inc., and Blake-Palm Elevator Co." Library of Congress Prints and Photographs. Accessed August 18, 2014. http://www.loc.gov/pictures/item/2005695832/
Garden Archives Correspondence.