Welcome to Fort Jefferson ...

Fort Jefferson is located in Monroe County<1>.

While we don't have a date for the founding of Fort Jefferson, you might consider that their post office opened in 1861.

A typical abbreviation for Fort Jefferson: Ft. Jefferson

Fort Jefferson is near sea level<2>.

Time Zone: Fort Jefferson lies in the Eastern Time Zone (EST/EDT) and observes daylight saving time

Area Codes for Fort Jefferson: 305, 645 & 786<3>

Communities Also Named Fort Jefferson ...

Using our Gazetteer, we found that there are 2 communities that are also named Fort Jefferson - they are located in Kentucky and Ohio.

For more information, see our Tidbits & Trivia Page for Fort Jefferson.

Adding Fort Jefferson to Our Gazetteer ...

We originally found mention of Fort Jefferson in both the FIPS-55 and the GNIS. For more information, see the FIPS and GNIS Codes sections on our Miscellaneous Page.

From our notes, the earliest published mention we've found for Fort Jefferson was in the document titled List of Post Offices from Cameron Blevins and Richard Helbock.<4>

From that list, the Fort Jefferson post office opened in 1861.

For more details, see References and Mentions for Fort Jefferson.

Footnotes ...

<1>	If you're interested in how the shape of Florida's counties, including Monroe, have changed over time, we recommend the Atlas of Historical County Boundaries.
<2>	The elevation is an estimate for the area around Fort Jefferson - it will be higher in some places and lower in others.
<3>	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 305 code has been Overlayed with one of the following codes: 645 or 786. New phone numbers in the Fort Jefferson area will be assigned with one of these codes: 305, 645 or 786. As a result, placing a call in the Fort Jefferson area will require 10-digit dialing (where you enter both the area code and then the phone number).
<4>	A copy of their list with background information can be found at: https://cblevins.github.io/us-post-offices/data-biography/