What is this and how do I get rid of it?

We moved into a 75+ year old home about 3 years ago.   The lawn was not cared for the year before we moved in.  I had overseeded with the rhizomatous tall fescue as there were lots of bare spots before finding this site.   Since then, I've been lurking on here and following the recommendations.  I mow at the highest setting of my reel mower (about 3 inches) and had put a layer of compost down last year.  I also use Ringers and Milky Spore (as there was a grub problem made worse by a hungry raccoon).  The lawn looks green and relatively healthy.  I have the dandelions under control with pulling them (which is therapeutic for me).  I've also recently started throwing down used coffee grounds from starbucks figuring that a little free organic material couldn't hurt.  My newest problem is the weed pictured below.  There are a few very thick patches.  They are a pain to pull as they have lots of runners and when I do pull them, bare patches of soil are left underneath so they are obviously out competing the grass.  I'm in the Chicagoland area and would welcome any advice.  This site is great.
Thanks

That, right there, is nearly as dangerous as dandelions.   Search around the patch until you find one with 4 leaves, that is the ringleader , and pull it out.  Give it a year or two after that, and surely the entire patch will die.  If you haven't rid yourself of this evil menace by then, call the good people at monsanto and they will be happy to assist you.

What you have is good ole clover. 

You can read more about it at the bottom of the lawn care article.

If you add a little fertilizer to your lawn, the grass will quickly outcompete the clover.

Some people plant clover in their lawn intentionally since clover can feed the grass.

Thanks Paul. Greatly appreciated.  I'll be picking up some more Ringer and spreading it again this weekend.  I take it I don't have to pull the stuff.  Any thoughts on the coffee grounds?  Is this a worthwhile endeavor?

Harpo12 wrote:
Thanks Paul. Greatly appreciated.  I'll be picking up some more Ringer and spreading it again this weekend.  I take it I don't have to pull the stuff.  Any thoughts on the coffee grounds?  Is this a worthwhile endeavor?

Free organic material is alway good in my book.  It has some low-grade N-value, but worms do love it, and I love the worms.  So I toss it around when I get some and I'm bored.

I dry my grounds a little ... well, I should say that I leave my grounds to the following day and then they just happen to be dry.  And then I have a little grounds-only bucket.  And I sprinkle it on my lawn when the season is right.  Otherwise it just goes on the compst pile.