The Mahoning Avenue Historic District (Boundary Increase), listed on the National Register of Historic Places in 1978, represents the architectural and civic evolution of Warren, Ohio, from its origins as a prominent Connecticut Western Reserve settlement to a thriving 19th-century industrial hub. Extending the boundaries of the original 1971 historic district, this expansion encompasses an exceptional concentration of well-preserved residential, religious, and civic structures lining Mahoning Avenue. The district serves as a visual timeline of American architectural history, showcasing magnificent high-style examples of Federal, Greek Revival, Gothic Revival, Italianate, and Queen Anne designs. These grand properties were constructed by the city's early mercantile, legal, and industrial elite, whose wealth and influence shaped the development of Trumbull County and the wider region.

The boundary increase solidified the preservation of the district's cohesive streetscape, incorporating key properties that illustrate Warren's transition into the late 19th and early 20th centuries. Notable landmarks within the broader district, such as the Greek Revival Kinsman House (1832) and the Romanesque Revival Warren City Hall (originally the Perkins House), anchor the historic corridor, while the added properties maintain the architectural integrity, historic setbacks, and residential character of this prestigious neighborhood. By documenting the lifestyles and civic contributions of influential local families, the expanded district stands as a testament to Warren's cultural, political, and economic prominence within northeast Ohio.