Portland Observatory
Built 1807. Added to the National Register in 1973, and a National Historic Landmark.
The record
| Property type | Building |
| Address | 138 Congress St., Portland, ME |
| County | Cumberland County |
| Listed | Apr 24, 1973 |
| Listed for | Community planning, Architecture, Communications |
| Level of significance | National |
| Also known as | Observatory |
| Reference number | 73000122 |
| Built | 1807 · more from the 1800s |
| Designations | National Historic Landmark, Historic Civil Engineering Landmark |
The nomination form, the document that argues why this place matters, is in the National Archives: Read the nomination ↗
Visiting
| Address | 138 Congress St., Portland, ME |
| Coordinates | 43.6653° N, 70.2483° W · Directions ↗ |
| Also in Portland | 99 listed places in Portland → · walking tour → |
Explore
Map
Nearby in Cumberland County
Local history books for Portland
We earn a small commission if you buy through these links. It does not change what we list.
Henry Wadsworth Longfellow in PortlandJohn William Babin and Allan M. Levinsky, 2015Find at Bookshop.org
Maine travel guides
Titles come from Open Library's catalog, matched by subject heading or by title.
Reference
Questions people ask
When was Portland Observatory listed on the National Register?
Apr 24, 1973. It is also a National Historic Landmark, the higher of the two designations.
Source: National Park Service
When was Portland Observatory built?
1807.
Source: Wikidata
Where is Portland Observatory?
138 Congress St., Portland, Cumberland County, Maine.
Source: National Park Service
Where is the nomination form for Portland Observatory?
The National Archives holds the nomination form, the document that made the case for listing.
Source: National Archives
Is there a wildfire near Portland Observatory right now?
1 active incident within 50 miles as of 2026-10-17, nearest South Jackman Rx, 47 miles away.
Source: Map
Sources
Name, location, type and dates come from the National Register office's spreadsheet of listed properties, because the Park Service's spatial data does not carry this listing. The map point comes from Wikidata. Construction date, architect, style, photograph and encyclopedia link come from Wikidata and Wikimedia Commons, matched on reference number 73000122. Nothing here is transcribed by hand. The nomination form and photographs ↗ at NPGallery are the original nomination as filed with the National Park Service, and the form is often the best description of the place.