In this area of the US, crab crass is considered a stubborn, pesky weed. It is seen in cracks in patio stones and lawns.
Some people get quite upset about crab grass on their lawns.
There are a number of products that can be spread on a lawn to get rid of crab grass. These must be applied in very early spring.
The thing about crab grass is that it seeds itself. If there are bare spots in a lawn in autumn, the crab grass will settle its seeds in for the winter. The following spring, the crab grass grows quickly.
This type of crab grass is called Digitaira sangunalis.
There are other kinds of crab grass.

All the pictures are from Wikimedia Commons. Except for one.

These three pictures are of the Digitaria sangunalis. This is the crab grass that makes grown people cry. The first two are by, Matt Lavan from Bozeman Montana, USA.

Digitaria_sanguinalis_(3874834370)_(2) Matt LAvan from Bozeman Montana USA WCDigitaria_sanguinalis_(3874835780) Matt Lavan from Boseman Montana USA WCBy, Richard Arthur Norman (1958-), English Wikipedia.

Crabgrass Richard Arthur Norton 1958 en wikiThe last three pictures are from Hawaii and were taken by Forest & Kim Starr.

These two pictures are of Digitaria ciliaris.

Starr_050404-5432_Digitaria_ciliaris Forest Kim Starr WCStarr_050223-4356_Digitaria_ciliaris Forest Kim Starr WCDigitaria insularis.

Starr_041127-1140_Digitaria_insularis Forest Kim Starr WC