Corner sight triangles across the DC area

What can I put near the corner of a corner lot? The rules differ at every jurisdiction line. Here is the short answer for each.

Disclaimer: This is general information, not legal or professional advice for any one property. Codes change. SetbackIQ is not a zoning determination, a permit, or a survey, and it does not replace an architect, engineer, or lawyer. Confirm with your building and zoning offices before you build, buy, or sign a contract.

Where	Short answer
Washington, DC	DC's zoning code has no corner sight-triangle rule for private yards. At corners, DDOT keeps the sight distance triangle in public space clear: anything other than trees, such as walls, fences, hedges and perennials, should be no more than 3 ft high, and street trees keep their lower branches trimmed to 8 ft.
Montgomery County, MD	On a corner lot in a residential zone, nothing over 3 ft above curb level within 15 ft of where the front and side street lines meet.
Prince George's County, MD	No fence or wall within the triangle formed by the street lines and points 25 ft from the intersection, or anywhere an agency finds it creates a traffic hazard.
Alexandria, VA	On a corner lot, nothing more than 4 ft above curb grade may sit inside the triangle formed by points 30 ft from the intersecting curb lines. Tree trunks are allowed if branches stay above 8 ft. The BAR can waive this in historic districts.
Arlington County, VA	On a corner lot in an R or RA district, keep the triangle formed by the street lines and a line joining points 25 ft from the corner clear between 3 ft and 10 ft above the curb. Plantings, fences and retaining walls all count.
Fairfax County, VA	On a corner lot, keep a triangle 30 ft along each street line clear between 3.5 ft and 10 ft above street grade. Fences, walls, shrubs and low branches all count.

Towns and cities inside these counties (for example, Rockville, Gaithersburg, Bowie, Laurel, Herndon, Vienna, and Falls Church) have their own rules.