Robinson Terminal South Excavation Update: Pioneer Mills, Part 2

Archaeologists exposed the foundations of Pioneer Mills and excavated the structure. Built in 1854 and burned in 1897, Pioneer Mills dominated the Alexandria waterfront for more than 50 years.

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Note: The information on this page reflects the state of knowledge when this update was written. Information may have changed. 

Pioneer Mills, Part 2

November 2017


The remains of Pioneer Mills have been fully uncovered and archaeologists are at work documenting the foundations and carefully disassembling the ruin. The mill's foundations measure 122' x 112' and in some places are more than 6' deep. This photo was taken next to the building at 2 Duke Street, looking east toward the Potomac River.

Alexandria, Virginia from the Maryland side of the Potomac, Alfred Waud, 1861.

Pioneer Mills can be seen just above and to the right of the sailboat in this detail of an 1861 sketch by New York Illustrated News special artist Alfred Waud. Drawings like this one and historic photographs of the mill building can help us better understand some of the archaeological and architectural features being uncovered here at Robinson Landing. 

Stone support piers

Stone PiersThese larger, regularly-spaced flat stones in the center of the mill are actually just the tops of stone piers that extend several feet underground. On top of these piers would have sat vertical wooden posts that would have carried the weight of the heavy mill, including its 12 pairs of millstones, machinery, barrels and sacks of flour and wheat, interior floors and walls, and slate roof. 

Brick engine pad and wheel pit

Brick PadThis large, heavy brick feature probably supported the mill’s locally-made Smith and Perkins steam engine. While only barely uncovered in this photograph, additional excavations have revealed a slot or trench in the center of this brick pad that would have housed the engine main wheel, which would have been connected to a large shaft that would have supplied the rest of the mill with power through a series of wheels and belts. 

Small support piers

SupportsOne interpretation of these two parallel rows of flat stones and narrow channel leading away from the wheel pit is that they could have supported this rotating shaft. Belts would have connected this shaft to each of the pairs of mill stones as well as any other mechanical equipment in the mill such as hoists, lifts, and baggers.


AdditionsThe smaller brick rooms seen along the northern and western edges of the mill structure (here along the left and bottom of this photograph) are early-20th century additions to the mill. Added sometime between 1912 and 1921, they were used by the Safety First Manufacturing Company as a cleaning room, a core room (for storage of metal casting supplies?), and an office. 


Archaeology TrenchesSharp-eyed observers will also note these two darker, parallel features cutting diagonally across the mill site (running up and down in the center of this photo). These are back-filled archaeology trenches originally opened in the summer to confirm the mill’s location prior to uncovering it.


Photogrammetry TargetThe strange black and white pattern seen here is actually a photogrammetry target. Photogrammetry is a technique that uses many, overlapping images of the same subject in order to create a three dimensional model of that object. If you look closely at the other photos of the mill here, you can see several more of them placed strategically across the mill foundations. These targets are similar to each other, but not identical. The differences in the patterns help aid archaeologists from Thunderbird Archeology to align over 2000 photographs of the ruins in order to create a photogrammetric model. 

Excavated foundation stones

Stacked Foundation Stone

After careful documentation and excavation, archaeologists are removing and stacking the Pioneer Mills foundation stones for potential reuse in future projects.