The mills in 2018.
|Alternative names||Jillson Mills, American Thread Company Willimantic Mills|
|Architectural style||Mixed usage|
|Serving railway||New York and New England Railroad|
JILLSON MILLS Latitude and Longitude:
|Built||First Building: 1824, Current Building: 1880/1910|
|Demolished||Mill #03, 1990's; Chimney, 2012-2014; Mill #4, 1995 (fire)|
|Floor area||221,000 square feet (20,500 m2)|
American Thread Company
|Architect||Marston, Phineas F.|
|MPS||Eastern Connecticut Mills MPS|
|NRHP reference #||14000434|
|Added to NRHP||July 30, 2014|
The Jillson Mills (Officially known as the Willimantic Linen Company Mill Complex) is a mill complex in Willimantic, Connecticut. The mills produced cotton thread throughout the lifespan of the operation of the mill. 
The mill was first built in 1824 in the same style as the current one by William Asa and Seth Jillson. In 1854 the old mill was purchased by investors from Hartford. They ended up forming the Willimantic Linen Company, even though they never produced linen.  The company ended up rebuilding the mill in 1880 to near its current state. The last mill built on the complex was built in 1910.  The mill ended up under control by the American Thread Company in 1898 due to the merger of the previous ownership of the mill.  The mill was closed in 1985 due to the company moving operations to the South. 
Mill #4 burned down in 1995 due to a fire caused by local children.   The wooden swing bridge connecting the mills was closed permanently shortly thereafter.  The mills lay dormant until the former grounds started to be purchased for commercial and residential purposes. ArtSpace currently has its Windham apartments located in this complex.  The old chimney was demolished between 2012-2014. 
The Garden on the Bridge is located in the complex of the former mills. It is a stone arch bridge built in 1857, that formerly was used for automobile until the Frog Bridge was opened in 2000.  It is currently a pedestrian bridge with flora all over, giving the bridge a natural look.  The bridge was temporarily closed until 2006 when it was reopened for its current purpose. 
The complex was added to the National Register of Historic Places on July 30, 2014 along with other historic mills across the section of the state.  This makes it the one of 22 on the list in the town of Windham. 
- National Register of Historic Places listings in Windham County, Connecticut — Documenting the NRHP addition of the mill.
- Windham Textile and History Museum — The museum nearby documenting about the mill's history.
- Willimantic Footbridge — The footbridge nearby built for employees for a safe route to the other side of the river.
- Willimantic Freight House and Office — Old place to ship freight coming from the mill.
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