This house price index is only for houses with Fannie or Freddie mortgages.
From the FHFA: FHFA House Price Index Up 0.3 Percent in April 2015
U.S. house prices rose in April, up 0.3 percent on a seasonally adjusted basis from the previous month, according to the Federal Housing Finance Agency (FHFA) monthly House Price Index (HPI). The previously reported 0.3 percent change in March remains unchanged.
The FHFA HPI is calculated using home sales price information from mortgages sold to or guaranteed by Fannie Mae and Freddie Mac. From April 2014 to April 2015, house prices were up 5.3 percent. The U.S. index is 2.3 percent below its March 2007 peak and is roughly the same as the February 2006 index level.
For the nine census divisions, seasonally adjusted monthly price changes from March 2015 to April 2015 ranged from -0.8 percent in the East North Central division to +1.4 percent in the West North Central division. The 12-month changes were all positive, ranging from +2.3 percent in the Middle Atlantic division to +7.5 percent in the Pacific division.
emphasis added
This graph is from the FHFA and shows nominal house prices in April were 2.3% below the March 2007 peak for this index.
However, these are nominal prices. In real terms (inflation adjusted), national prices are still around 20% below the previous peak.