“Location, location, location” did not become the most overused slogan in real estate without reason: a property’s surroundings are as important as the property itself. So for decades, most commercial brokerage firms have had full-time canvassers or even entire departments of agents relentlessly pacing city blocks to keep up-to-date maps of fast-changing storefront businesses.

But in recent months, several brokerage houses, including Massey Knakal Realty Services and the Winick Realty Group, have embraced a Web site called CityMaps.com, which has mapped all the storefront businesses on New York City’s streets and tries to keep them current.

“It’s a tool that I would have to say I use pretty much on a day-to-day basis,” said Jill Lovatt, a director of retail leasing at Massey Knakal. Ms. Lovatt said that when she had a retail space to lease, she used CityMaps to determine what retail uses already existed in the neighborhood, so she could find the best potential tenants.

She said she also used the maps to reach out to nearby retailers to see if they were interested in moving to a new space or had any expansion plans.