It's likely VDOT. But going to them directly does not get the issue resolved quickly. Check out who your local elected official is for the county and contact their office.
http://www.fairfaxcounty.gov/government/board/

The chariman-at-large is Sharon Bulova and there's individuals for each district. During that horrible snow storm a few years ago, a front end loader who was clearing the snow from the side of the street actually picked up a large section of the sidewalk and deposited it in our front yard. I contacted our district supervisor's office and it got fixed relatively quickly. Gotta love our elected officials!

The city should fix it. In Montgomery County, we called 311. It took a while but a crew eventually showed up and fixed it.

9:22 - that is not true. We knew people in McLean that were such PITAs (they complained ALL. THE. TIME. about nothing), when it came time to remove a tree down, on a side street in a storm, VDOT put them on the BOTTOM of the list!

I actually agree, since it was a side street anyway, but you get the idea. No one likes a whiner, and certain areas are FULL of them. If only they realized that gets them no where fast.

If you are in the rich part they will fix it fast. I think it might be vdot.

Fairfax county sucks. Its too big and poorly managed. Look on the county web page, there may be help there, OP. GL.

Sidewalks? What sidewalks? I wish I could get FFX County to actually put in some sidewalks around here. The county really lags Arlington in that area

There's a patch on our sidewalk that needs to be fixed. We do not live in an HOA. In Fairfax county, is this the responsibility of the homeowner or the county? If it is the county, which division do I call?