28 April 2016

Finding and Interpreting Historical Aerial Photographs to Inform the History of Your House

When attempting to determine an exact construction date for a home, we often turn to maps to aid in this effort. This is, of course, as a form of visual/graphic evidence in conjunction with other documentary evidence, such as deeds, mortgages, etc. Not to be overlooked, however, are historical aerial photographs. In the same way that maps from various years can help to narrow down a range of possible construction dates or to observe development of a neighborhood over time, aerial photographs can provide a literal and visual representation. The key, as with maps, is knowing where to look and how to interpret the images found. While the ideal scenario would be to find at least one dated image prior to the house's construction and be able to compare it to one or several images post-construction, this would not be possible if the house you are researching is older than about 1920. Still, it is likely that aerial photographs exist for your home dating back several decades and thus still extremely interesting and useful to examine for your research.

A circa 1928 aerial photograph of my neighborhood, located via PhilaGeoHistory. My house is highlighted with the purple arrow, about 5 years after its construction.

A Brief History of Aerial Photography

Aerial photography has been linked to the documentation of our built environment ever since its invention in the mid-19th century. According to the Professional Aerial Photographers Association, early aerial images were taken over Paris and Boston by pioineers in hot-air balloons in the 1850's and 60's. Over the next fifty years, photographers continued aerial experiments, strapping cameras to rockets, kites, and even pigeons. By World War I, photos were being taken from another recent invention, airplanes, and were regularly used to document battle maps during the War. Due to further technological innovation, largely by Sherman Fairchild both during and after WWI, aerial photography became adopted and popular for wide government, civilian, and commercial use starting in the 1920's. Nowadays, satellites capture the bulk of aerial imagery, but the moments in times past which we wish to view here would have been taken from airplanes.

Sources for Aerial Photographs

Places to inquire about aerial photographs throughout the past 90 or so years include libraries and historical societies, which can possibly point you to more specific repositories or quasi-governmental agencies or planning authorities. The latter may have commissioned aerial photography in your area for regional planning purposes at several points in time.

Many of these may ultimately be available to access online. Try a Google search for "historical aerial photographs (your state/city)" and you might run across a government agency or library with a stash of old aerials. Locally (to me), the PhilaGeoHistory website run by the Philadelphia Athenaeum includes a section of aerial photographs not just the City of Philadelphia but for the metropolitan area at large. The United States Geological Survey (USGS) has a plethora of satellite and aerial imagery available, including an entire section of "Historical Photographs" from 1937 to the present. A link leads to the USGS Earth Explorer image search where you can search by address, then select different checkboxes under "Data Sets" to see if you can find any of those images for your area. Basic resolution images are free to download, whereas high-resolution images are available for a fee.

A number of commercial websites are available as well. Google Earth is likely the most well-known, has some historical imagery (in Google Earth 5 and later), and also has a neat "slider" feature which allows you to slide back and forth between images from different years. Most of the images in Google Earth appear to be fairly recent (1990 or later).

Screenshot of Google Earth historical imagery. The "slider" is shown at the upper left. The earliest available image for my neighborhood on Google Earth was from 1992 (and the roof of my house is washed out in the low-resolution image, rendering it difficult to see. Image quality varies from year-to-year.
Two other commercial sites worth checking out are www.historicaerials.com and www.vintageaerial.com.

The homepage of Historic Aerials displays a map of the United States covered in two shades of green-- the dark green areas have "historic" images available, whereas the remainder only have aerial photos from 1990 or later. Although the website considers anything before 1990 "historic", I've found that many of the shaded areas have available images back to the 1920's and 1930's, with several years in between available. It is quite easy to navigate from year to year at a specific location. The only difficulty is the large watermark which can make it difficult to view detail and only goes away if you purchase the image.

Screenshot at the homepage of Historic Aerials. Although images are generally available throughout the United States, the areas marked in the darker green are more likely to have earlier and older images available.
Screenshot on the image viewer at Historic Aerials. For my neighborhood, images are available to view for 13 different years, spanning from 1948 to 2013.
Vintage Aerial is a very unique website, focusing on rural areas and small townships, and their collection of images are oblique views (rather than a straight-down bird's eye view), which is a neat perspective. One can select any county in the U.S. and the results will tell you if their archive includes images from that county, as well as from which years. It appears that manually browsing images by film roll is the only way to view them at this time, but it is relatively simple to pick a film roll and scroll through the images in the roll. As for finding the right roll, many archive years are accompanied by a "flight map" of the county which includes a guide (which appears to be hand-marked by the original photographer), marking the coverage areas of each film roll. Locate the area on the map you are seeking and hopefully a flight path is marked with a film roll number. Navigate back to the list of film rolls from that year and choose the correct film roll to scroll through the images.

1964 Flight map from Vintage Aerials website in Montgomery County, PA. This map marks each film roll's coverage. The image below was found in Film Roll 88.
Although there do not appear to be any aerials from my particular neighborhood, I did find images from 1964 from the street where I grew up, but not my house's exact location. I was able to locate this image of a huge Victorian house I've always admired, about a mile from the house in which I grew up.

1964 image of a Victorian-era home, found in Film Roll 88 under Montgomery County at Vintage Aerial.

Finding Useful Information in Aerial Images

As you gather images from various years, you will find a wide range of image clarity-- even an image from as recent as the 1990's may not be as clear as an image from 1930. Within the last decade or so, however, satellite imagery has become extremely clear. The most helpful aid which a series of aerial photos could provide would be to help pinpoint the year of construction of a house. If you happen to find an image from 1948 and a house does not exist in it, but it does appear in a 1950 image, then you know that the house was constructed sometime from 1948-1950. This image below is a comparison between a circa 1928 image and a circa 1930 image. Houses which appear on the later image, but not on the earlier image we know were recently constructed as of the date of the second image.

The houses marked by the arrow in the 1930 image were recently completed as of that date, since they did not exist at all in 1928.
As mentioned previously, since aerial photography did not become common until the 1920's, if the house you are researching is older than that, then you will not be able to find images for this purpose, but viewing and examining what you can find will still be useful and interesting.

You may recall from my previous posts that I believe the construction date of my house to be between May 1922 and November 1923 based on numerous types of documentation and analysis. The earliest aerial photograph I was able to locate for my neighborhood was an image labeled circa 1928 (found via PhilaGeoHistory, as part of the collection of the Free Library of Philadelphia). There are no images from prior to my house's construction, but it is still neat to see photographic evidence of the house's existence this early, only a few years after its construction.

Portion of an image, located via PhilaGeoHistory. My house highlighted with purple arrow.
Although the resolution of the image is not extremely clear, you can see the house as one of the few existing on this portion of Central Avenue, something that further confirms evidence found in early atlas maps. The lightly-colored area is actually my entire current property, with the actual house only distinguished by a shadow line at the back of the house. The reason why the whole lot is lighter than other undeveloped lots may be that grass and other growth may have been cleared off of the property and had not yet re-grown, or had regrown in a distinctly visual way.

What you also notice here is the loose outline of a tree line running from northwest to southeast just along my property line, continuing on along multiple properties. This tree line then turns northeast a few blocks away, on either side. To see the reason, see this clip from a 1916 atlas map.

Portion of a 1916 atlas map, via Franklin Maps. My house's location highlighted in purple.
We can also zoom out on the c. 1928 aerial image.

Portion of a c. 1928 aerial image, located via PhilaGeoHistory. To the right, the Spear tract is highlighted with a purple boundary. To the left, we see how a tree line defined much of this boundary.
Although the map is oriented to align with the property, this 1916 map is the latest which depicts the land tract previously owned by Emma Spear. In 1919, she sold this land to Philadelphia jeweler Reginald Ferguson, who subdivided the land into individual home lots. The tree lines in the c. 1928 aerial image correspond to the border of Spear's former land. In the aerial image, we see that this land has only sparsely been developed in the preceding 7 or 8 years, although most of the streets have been laid out (although nearly certainly unpaved) to align with other existing roadways. The 1928 photograph also shows us the already-established residential development to the southwest (labeled "North Glenside" to the left in the 1916 map).

Jumping ahead in time to 1959, some of this tree line remains, and you can see that the neighborhood of Ardsley has now been largely filled with single-family homes throughout. Suburbia has taken hold.

Aerial image of the Ardsley neighborhood, 1959. Located via PhilaGeoHistory.
Zooming in on my house now.

Most of my neighbors' houses have now been built prior to this 1959 image, including the long row of stone-fronted Cape houses running to the southwest. The exception is the ranch house on the north side which was built in the 1970's. You can see the empty lot adjacent to my house which at the time of this image was owned by the owners of my house, the Cantlins. This image was also captured at least a decade after the Cantlins expanded the size of this house-- the purple arrow points to the rear addition constructed in the 1940's.

Have Fun!

These types of images should not be overlooked as part of the historical analysis of your house's history. They are an extremely fascinating way to gain photographic and visual evidence of the evolution of both your house and its context within the greater neighborhood. See if you can locate multiple aerial images over time for your home, and have fun taking a peek at these literal snapshots in time!

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