Starting with the 2005-02-16 release, the series reflects an increase in the universe of permit-issuing places from 19,000 to 20,000 places.
Source: US. Bureau of the Census
Release: New Residential Construction
US. Bureau of the Census, New Private Housing Units Authorized by Building Permits in the West Census Region [PERMITW], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/PERMITW/, August 29, 2015.