The Mary Fessler Papers span the years ca. 1940-2001, with the bulk of the material dating from 1968-1984. They are arranged into the following series: Personal Papers, ca. 1940-2001; Montgomery County League of Women Voters, 1948-1980; Montgomery County Democratic Committee, 1967-1993; Ninth-District Democratic Committee, 1979-1981; Montgomery County Board of Supervisors, 1968-1998; and Blacksburg Library Building Committee, 1994-1999.

The Montgomery County Board of Supervisors series spans the period 1968-1998 (bulk 1977-1984) and is the largest series in the collection. It is comprised of the following subseries: Minutes, 1977-1984; Correspondence, 1978-1985; Financial Records, 1977-1995; Subject Series, 1968-1998; Annual Reports, 1976-1982; Publications, 1974-1984; Capital Improvements Program Committee, 1978-1987; Montgomery County Community Services Organization, 1974-1979; Montgomery County Planning Commission, 1976-1989; and Montgomery County Public Service Authority, 1969-1973.

Minutes contain Fessler's copies of the official minutes of Board of Supervisor meetings for the period 1977-1984; they also include copies of agendas and official reports submitted to the Board. Correspondence is comprised of letters Fessler received pertaining to county government issues. It is organized into Incoming Correspondence, Inter-office Correspondence, both arranged chronologically; and Correspondence Regarding, arranged alphabetically by subject. Financial Records are comprised of Fessler's copies of budget requests, county revenue projections, and financial reports and analyses. The Capital Improvements Program Committee, Montgomery County Community Services Organization, Montgomery County Planning Commission, and Montgomery County Public Service Authority series are comprised of copies of records of these agencies that were sent to Fessler when she was a member of the Board of Supervisors.

Subject Series, the largest subseries within the Montgomery County Board of Supervisors series, are comprised of materials Fessler collected and filed by subject and document issues of concern to her during her tenure on the Board. They files contain a variety of materials, including copies of county government documents, correspondence with the county government staff, reports, studies, and clippings. Notable subjects include construction of the Roanoke River dam, landfills, and planning for sewage, water, and refuse.

The Montgomery County Democratic Committee series spans the period 1971-1993 and documents the committee's work in support of local, regional, and state Democratic candidates from 1867 to 1971, 1979 to 1981, and in 1993, and Democratic Party conventions. The records are comprised primarily of correspondence, get-out-the-vote materials, and newspaper clippings. Included is a file of correspondence and clippings pertaining to the activities of the state legislature from 1971 to 1974, a file on the re-drawing of magisterial districts in Montgomery County in 1972, and a folder of statistics on the race of registered voters, by precinct, in Montgomery County, 1979 to 1981.

The Ninth-District Democratic Committee series dates from 1977-1981 and is comprised primarily of correspondence from officials of the state Democratic Party and members of the local and regional committees; it also includes ephemera from Democratic campaigns from the period 1980 to 1981. A frequent correspondent is state Democratic Party Chair Richard Davis.

The Montgomery County League of Women Voters series spans the period 1948 to 1980 (bulk 1970-1980). Just one folder, it is comprised primarily of small publications put out by the League of Women Voters in the early 1970s promoting ratification of the Equal Rights Amendment.

The collection also includes a small series of Personal Papers that span the period ca. 1940-2001. They include a photograph of Fessler, ca. 1940, and a folder of thank-you letters from Virginia Governor Gerald Baliles, Lieutenant Governor Dick Davis, Delegate Rick Boucher, and Attorney General Mary Sue Terry.