n. The area that a person can comfortably or conveniently cover on foot.
In many parts of the country, walking has become as quaint a pastime as spinning yarn or playing the bagpipes. Between 1977 and 1995, the number of daily walking trips taken by adults declined by 40 percent — while more than a quarter of all car trips are now shorter than a mile. Those under-a-mile journeys fall into the zone that new urbanists call ''walkshed'': the area a person can reasonably cover on foot. People whose walksheds teem with shops and restaurants have more reason to walk than those whose don't.
—Dashka Slater, “Walk the walk,” The New York Times, April 20, 2008
Could we make it without a car?

For thoughts on this, I called Alan Durning, a Seattle native and father of three who has been surviving without a family car since February. …

They bought a membership in a car-sharing service similar to the Twin Cities' HourCar and ZipCar. And then they concentrated most of their errands and outings within what Durning calls a "walkshed" — the 248 businesses, services and entertainments to be found within a one-mile radius of their home.
—Laura Billings, “Escaping a life behind the wheel,” Saint Paul Pioneer Press, July 16, 2006
2006 (earliest)
A one-mile perimeter, therefore, defines this car-less family’s pedestrian travel zone — call it our "walkshed." Fortunately, because we chose to live in a compact community, our walkshed turns out to be well stocked.
—Alan Durning, “One Mile from Home,” The Daily Score, April 05, 2006
The word walkshed is a kind of urban take on watershed (1803), the area of land that drains into a large water source, such as a river, lake, or ocean. The watershed uses the source as the starting point and extends to cover all the land that supplies that source with water. In a similar way, your walkshed begins at a particular point (such as your home or office) and extends to cover all the land that you can reasonably reach on foot.