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.

The Harriet Taylor Upton House, located on Mahoning Avenue in Warren, Ohio, holds exceptional national significance as the home of prominent suffragist Harriet Taylor Upton and, for a time, the temporary headquarters of the National American Woman Suffrage Association (NAWSA). Originally constructed around 1840 in a transitional style reflecting both Federal and Greek Revival influences, the house became Upton's residence in 1887. From 1903 to 1905, while Upton served as the national treasurer of NAWSA, she relocated the organization's headquarters to Warren and operated its business directly out of this home. During these years, the residence served as the nerve center for the national suffrage movement, where vital campaigns were strategized, correspondence was managed, and political literature was produced and distributed across the United States.

Beyond its administrative role, the house is deeply tied to the personal legacy of Harriet Taylor Upton, one of the early 20th century's most influential civil rights leaders and political organizers. Upton's tireless work at the local, state, and national levels brought prominent suffrage figures, including Susan B. Anthony and Carrie Chapman Catt, to the Warren home to plan their national crusade. Following the ratification of the Nineteenth Amendment in 1920, Upton continued her trailblazing career by becoming the first woman to vice-chair the Republican National Executive Committee. Designated a National Historic Landmark in 1992, the Harriet Taylor Upton House stands as a physical monument to the dedication of the women who secured the right to vote and remains open to the public as a historic house museum.