Hi, it's hard to say from a picture on the internet, but that might be barnyard grass because of the reddish-purple stems near the base of the grass close to the ground. If it's barnyard grass, it's easy to pull out because of its shallow root system.

Barnyard grass is a warm-season annual that reproduces by seed. It's a grassy weed, not a broadleaf weed, so you won't be able to use the 2,4-D in Weed-b-Gon to get rid of it. The Scotts Lawns book says:

"Kill mats by spot-treating with a nonselective herbicide. Repeat the treatment two more times at intervals of 7 to 10 days, until plants die."

Notice that the Scotts company's book says to kill MATS of this stuff. I guess that's because if you use a nonselective herbicide like Roundup on individual barnyard weeds surrounded by grass, you'll also kill some of the surrounding grass. Really, the Scotts book should have said to just pull this stuff out. It pulls out very easily--shallow roots. And it's a lot faster and safer than having to spray 3 times every 7 to 10 days. And remember that's for Mats. Let us know how it turns out.

Thanks for the info. I pulled a bunch of them out last weekend and they definitely had the purple stem near the base and the roots were shallow. I barely made a dent however. This weed seems to be invading our whole neighborhood this year. Our lawn is in bad shape this year and I still have a bunch of them along the sidewalk. I heard the Weed-B-Gon with crabgrass control (quinclorac) can help and will try that out next.

Looks like either Johnson or Barnyard grass. Really does not matter what it is as the treatment is the exact same for all grassy broadleaf weeds, so don't get hung up on trying to identify the exact species. Whatever you do, do not let it go to seed.