144606
The proving ground was in operation from 1941 to 1945 and was a major employer of Hempstead , Howard , Nevada , Clark and Lafayette counties .
 location: Hempstead
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Hempstead 
Answer:
 location: Hempstead