Zillow, the nation's largest real estate listings website, paid $50 million in cash Monday to acquire StreetEasy, another listings site based in New York City. 

The deal should help Zillow stay competitive in the market, which StreetEasy had in the bag with 1.2 million monthly unique users and listings with some of the city's premiere brokerage firms.

Talks of a merger began three years ago, but nothing came of it until Monday. As part of the deal, StreetEasy will keep its name but continue to function separately, though Zillow has plans to step up its mobile presence through apps. 

StreetEasy, which Michael Smith and Sebastian Delmont launched in 2006, quickly made a name for itself in areas such as New York City, the Hamptons, northern New Jersey, Philadelphia, Washington D.C., and southern Florida. But New York real estate was its specialty, due to the listings and easy-to-use search filters such as "Near Specific Subway" and "Zoned for School."

Zillow, which is based in Seattle, Washington, has increased its stock price 166 percent since going public in 2011 and reported second quarter revenue of $46.9 million. Currently, the site has 61 million unique visitors --a 66 percent uptick from last year.