The District’s Shepherd Park and Petworth neighborhoods saw the biggest year-over-year gain in housing prices last month, with the average selling price of a house or a condo up 42 percent from a year ago.

Monthly data from Long & Foster Real Estate Inc. shows the median sale price in Petworth last month was $499,900. The number of active listings in the Petworth area is down 38 percent from a year ago, and sellers last month got an average of 100.7 percent of asking price.

Chevy Chase, D.C., faired best for sellers in May, with the average contract price 103.2 percent of list price. Chevy Chase also had the highest median sales price in the District last month, at $855,000.

Houses and condos are selling the fastest in Logan and Dupont Circles, on the market an average of just 14 days last month. The Penn Quarter was close behind, with an average Days on Market of 15 days.

District-wide, the median selling price last month was up 9 percent from a year ago, to $489,000.