A Closer Look at North Potomac and Its Relationship to Gaithersburg. By MCS Staff, The MOCOSHOW. 25 March 2026
Anytime North Potomac comes up (North Bethesda too, but that’s a conversation for another day), the most-liked reply is almost always some version of, “You mean Gaithersburg?” Let’s get into it.
In the summer of 1989, the U.S. Postal Service approved “North Potomac” as an acceptable name for some addresses in the 20878 zip code that were not in the City of Gaithersburg, which had historically defaulted all addresses to Gaithersburg. That’s where a lot of the confusion starts.
North Potomac has never been part of the City of Gaithersburg. It’s unincorporated, meaning it’s governed directly by Montgomery County, not the city. It doesn’t receive city services, residents don’t pay Gaithersburg city taxes, and they don’t vote in city elections. So even if your address says “Gaithersburg, MD 20878,” that’s just the post office designation. It doesn’t necessarily mean you live within Gaithersburg city limits. The United States Census Bureau has recognized North Potomac as a census-designated place in every census since 1990.
Geographically, North Potomac sits north of the Potomac River in west-central Montgomery County, about 20 miles from DC. It’s bordered by Gaithersburg to the north, Rockville to the east, Travilah to the south, and Darnestown to the west. Potomac itself sits southeast, with Travilah in between. In addition to the 20878 area code, parts of 20850 can also be in what’s considered North Potomac while sharing an area code with homes in Rockville.
Planning-wise, they’re treated differently too. The Maryland-National Capital Park and Planning Commission places North Potomac in the Potomac Subregion Master Plan, while Gaithersburg operates under its own independent city planning and zoning. Over the years, Gaithersburg has expanded through annexation, bringing areas like Kentlands and Lakelands into the city. North Potomac was never annexed and remains under county jurisdiction.
Back in 1989, The Washington Post described the area as something of an identity puzzle. One resident put it simply… it wasn’t Potomac, Rockville, Gaithersburg, or Darnestown. That ambiguity is exactly what led to the push for a name.
Some have questioned whether the name “North Potomac” was driven by real estate interests. While some local realtors say the name can be appealing from a marketing standpoint, most note it’s just one small factor. Several agents have also shared that while the name has certainly been embraced over time, the original push for it came from a grassroots effort by homeowners.
Per the WaPo article, the name “North Potomac” was formally adopted after a community association vote of 200 to 4 in 1988. Other options like “South Gaithersburg” were never seriously considered, and “Travilah” was reportedly dismissed due to its association with the nearby rock quarry and heavy truck traffic. At the time, community leaders emphasized that the goal wasn’t to rebrand or distance the area from Gaithersburg, but to establish a clearer sense of identity. As association president Robbie Milberg put it, the effort was about defining the community, not reshaping its image.
So depending on how you look at it, everyone has a point. North Potomac isn’t a city, and it’s not part of Gaithersburg. It’s a distinct, unincorporated part of Montgomery County with its own identity, even if the mailing address still throws people off.
That said, many will always consider it part of the greater Gaithersburg area, especially given the shared 20878 zip code. It’s not all that different from places like Flower Hill (20879), which are commonly associated with Gaithersburg and share a zip code with addresses in the city, but are not actually within the city limits. North Potomac and Flower Hill are separated by a 20-25 minute drive without traffic.