Granite Manufacturing Mill Site (18BA196)

The Granite Manufacturing Mill Site (18BA196) is the location of an early 19th-century iron works and nail factory (the Ellicott Rolling and Slitting mill complex) that was replaced in the late 19th century with a cotton and textile mill (the Granite Mill complex). The site is located on the Patapsco River in the town of Oella in Baltimore County.

The Ellicott Iron Rolling and Slitting Mill opened in the first decade of the 1800s. The mill complex consisted of two buildings: a 2-story frame building thought to be the slitting mill and the smaller stone structure that was probably the nail factory. Prior to 1838, the iron works added a furnace for rolling copper sheets. Investors purchased the site after forming the Granite Manufacturing Company in 1843. By 1846, a 4-story granite mill building with a tower had been constructed. They apparently used the pre-existing mill dam and raceway constructed for the iron works. The complex consisted of the cotton mill, a machine shop, and a foundry. The mill was quickly rebuilt after a fire in 1866, but following a damaging flood in 1868, it was never rebuilt.

In 1981, Phase I/II investigations were conducted within the proposed right of way of the Oella Sewer Project. Fieldwork included pedestrian survey and mechanical trenching in the area of the mill complex. A 17 ft section of a mortared stone wall running NW-SE was encountered in the northern section of the trench, as well as another 4 ft section of the wall farther south in the trench. Since portions of the 19th-century mill complex, such as the mill race and possible structural walls, appeared to have remained intact, a Phase III data recovery program was initiated in 1982.

A second wall, interpreted to be the outside raceway retaining wall, was located 17 ft east of the first wall. At the southern end of the main trench, the wall curved slightly to the west before it abruptly stopped. Excavation along the western or river side of the main trench encountered two stone walls that ran perpendicular to the wall in the main trench (the west raceway retaining wall).

Trenches #4 and #9 were excavated to determine the extent of the perpendicular walls. The southern wall (excavated by Trench #4) was found to contain 2 intact, cut-stone window sills and a cut-stone door sill, as well as another corner of a the wall at the western end of the trench. The interior of the south wall was faced with plaster. Trench #8 was excavated in order to expose the western wall. It then became clear that the wall uncovered in the main trench was the eastern wall of a structure that adjoined the raceway wall. The wall shared by the structure and the raceway was wider than the rest of the raceway wall.

Based on the dimensions of the exposed walls, the structure was determined to have been the Granite Factory machine shop. A trench excavated on the interior of the east wall showed that the wall reached a depth of 66” below the top of the wall. Approximately 3 ft. of fill sat above what was perceived to be strata related to the use of the building. A layer of brick and rubble, above an ash layer, which sat on top of a coal layer were possibly related to the 1866 fire that destroyed the adjacent factory. The floor of the building contained iron nodules and slag from iron working. In the southeast corner of the building, a group of metal bands were located, supporting documentation that barrel hoops were made at the location.

At the west end of Trench #4, south of the wall, excavations in Trench #5 encountered sections of another rectangular structure. The cut granite walls were mortared and the east wall exterior had been finished with mounded and sharpened mortar that was painted with a black tar-like substance. The excavators referred to this building as the “nail factory” that was suggested to have functioned as part of the Ellicott Rolling and Slitting Mill. Its construction differs from, and possibly predates, the machine shop. It is unclear what the function of the building may have been after the Granite Manufacturing Company took over the property.

The east wall of the “nail factory” terminated at a large, circular structure 6 m in diameter, built of cut stone and lined with two layers of brick. An oily substance with a distinct odor was present on the base of the feature and at the top of the walls. The function of the structure was interpreted as a container for gas, possibly coal oil gas, for use in lighting the Granite Factory.

Excavations in Trench #7 revealed a stone wall to represent the remains of the Granite Manufacturing Company textile mill. It is located at a point to the northwest of the race spillway where it could have contained two water wheels.

The Granite Manufacturing Mill Site (18BA196) is the location of an early 19th century iron works and nail factory (the Ellicott Rolling and Slitting mill complex) that was replaced in the late 19th century with a cotton and textile mill (the Granite mill complex). The 19th century mills were an important part of the industrial development of Baltimore County along the Patapsco River. Archaeological investigations resulted in exposing large portions of a raceway, a section of the “nail factory” associated with the ca. 1806 Ellicott complex, and portions of 3 buildings related to the operations of the ca. 1846 cotton/textile mill.

(Edited from the Maryland Historical Trust Synthesis Project)


  • Thomas, Ronald A., and Judson Kratzer
  • 1982. Archaeological Data Recovery at the Granite Factory, Oella, Maryland. MAAR Associates, Inc., Newark, Delaware.

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