Sentence:  To find out , we traveled throughout that part of Laos still nominally controlled , in the daytime at least , by the Royal Lao Army : from Attopeu , the City of Buffalo Dung in the southeast , to Muong Sing , the City of Lions in the <WSD>northwest</WSD> , close to Communist China ( map , page 250 ) . 
Meaning of the word marked with <WSD> tags:  the northwestern region of the United States