Greater Des Moines house sales and prices dropped in February on a month-to-month basis, but remained above year-ago levels, according to the Des Moines Area Association of Realtors. The median price of the 731 homes that sold last month was $186,000. In January, 741 houses sold at a median price of $188,500. A year ago, 690 houses sold at a median price of $169,000. Pending sales increased in February to 1,081 from 987 in January. Houses that sold last month had been on the market an average of 81 days, compared with 73 in January and 83 a year ago.