Footnotes ...

<1>	When there's a risk of an area code running out of phone numbers, an 'Overlay Area Code' is created that has the same geographic boundaries as the existing area code. In this case, the 410 code has been Overlayed with one of the following codes: 443 or 667. New phone numbers in the Gwynn Oak area will be assigned with one of these codes: 410, 443 or 667. As a result, placing a call in the Gwynn Oak area will require 10-digit dialing (where you enter both the area code and then the phone number).
<2>	ZIP Codes have been created by the United States Postal Service (USPS) as a way of grouping addresses to make delivery more efficient. The boundaries of the ZIP Code can be changed, re-assigned, eliminated or overlapped with other ZIP Codes. So keep in mind that any given ZIP Code is only 'loosely' associated with a community (such as Gwynn Oak). When looking for a ZIP Code, whether Gwynn Oak or elsewhere, it's always best to check the website of the United States Postal Service (USPS).
<3>	The elevation is an estimate for the area around Gwynn Oak - it will be higher in some places and lower in others.
<4>	Longitude & latitude values may not be the geographic center of Gwynn Oak, rather it may be a prominent intersection or the center of population, etc. It will vary depending on the source.
<5>	Name of the USGS 7.5 Minute topographic map which includes Gwynn Oak.
<6>	Every year, the US Census Bureau creates a population estimate for the preceeding year. Keep in mind that this value is an estimate and not an actual count. The most recent Census estimate is for the year 2019.