The Union Mill Complex, (also Bischoff's Chocolate Factory), is located at the junction of Milton Avenue (NY 50) and Prospect Street in Ballston Spa, New York, United States.

The property is a wedge-shaped parcel with Milton Avenue on the east, the Kayaderosseras Creek on the north and Prospect Street to the south and west.

The mill itself is an L-shaped four-story building with two stair towers in the late Second Empire style, with corbeled brickwork and cast iron detailing.

The east tower has a clock face in one dormer and a 1,500-pound (680 kg) bell, cast by Jones & Co. of Troy.

Brezee, features oak and cherry wainscoting, a highly decorated cashier's desk and walk-in vault.

Similarly, the bag factory has a wainscoted cashier's office with pay windows, staircase with two open flight and varnished newel posts with turned balusters.

George West had profited during the Civil War when he invented the flat-bottomed paper bag, the first which could hold as much as 50 pounds (23 kg).

After the fire he bought the property and built the current structure, renaming it the Union Paper Mill.

His chocolate company had outgrown its original location in Brooklyn and needed new space quickly.

[3] A Philadelphia firm renovated the interiors extensively for its new use and shored up the mill with steel and reinforced concrete.

[1] Bischoff installed colored lights to illuminate the water falling over the dam and made other improvements to the immediate vicinity.

In 1997 the complex underwent extensive interior renovation and was converted into space for small retailers, professional offices, and a restaurant.