 = Washington State Route 221 = 
 
 State Route 221 ( SR 221 ) is a 25 @.@ 95 @-@ mile ( 41 @.@ 76 km ) long state highway located entirely within Benton County , Washington , United States . The highway serves to connect the unincorporated community of Paterson to the county seat Prosser . The highway has existed since at least 1926 and was designated as Primary State Highway 8E from 1937 until the 1964 renumbering of Washington state highways . 
 
 = = Route description = = 
 
 Washington State Route 221 ( SR 221 ) starts at an intersection with SR 14 in the unincorporated community of Paterson . After leaving Paterson the highway travels north through rural farm land as a two @-@ lane highway . A few minor roads are intersected before the roadway turns to the west after about 17 mi ( 27 km ) , before turning back to the north . After the highway resumes its northerly course it climbs into the Horse Heaven Hills , gaining a passing lane through the uphill segments , before finally terminating at SR 22 in south Prosser . 
 Every year the Washington State Department of Transportation ( WSDOT ) conducts a series of surveys on its highways in the state to measure traffic volume . This is expressed in terms of average annual daily traffic ( AADT ) , which is a measure of traffic volume for any average day of the year . In 2009 , WSDOT calculated that as few as 2 @,@ 000 cars traveled through the central part of the highway , and as many as 2 @,@ 500 cars at the interchange with SR 22 . 
 
 = = History = = 
 
 The roadway on its current alignment has existed since at least 1926 , however there are records of a road between Paterson and Prosser since 1906 . The highway was designated Secondary State Highway 8E ( SSH 8E ) in 1937 , but the route number was changed to SR 221 during the 1964 state highway renumbering . 
 High winds have forced the closure of SR 221 in 2003 , 2004 , and 2005 due to large amounts of dust being blown around , causing visibility to drop to almost zero through the Horse Heaven Hills . 
 
 = = Major intersections = = 
 
 The entire highway is within unincorporated Benton County . 
 
 