[22][23] Located on the northern end of the Somerset Hills region, the borough is known for its country homes and historic downtown.

[29] Notable landmarks in the district include the Phoenix House, which serves as the borough's municipal building, along with the Black Horse Inn Tavern & Pub; New Jersey’s oldest continually operating restaurant, dating back to 1742.

[33] In the Forbes magazine's 2006 (209th; median sale price of $835,000) and 2012 (356th; $800,672) rankings of the Most Expensive ZIP Codes in the United States, Mendham was listed among the top 500 nationwide.

[38][39] Mendham Borough was incorporated by an act of the New Jersey Legislature on May 15, 1906, from portions of Mendham Township, because residents of what became the borough wanted sidewalks and street lights constructed while those that lived in what remained the township (including the communities of Brookside and Ralston) felt it was cost prohibitive in their more rural areas.

[24] Located on the borough's southern slope of Bernardsville Mountain in the Somerset Hills lies Wendover, the former estate of investment banker Walter Phelps Bliss (1870-1924).

[43][44] Phoenix House was purchased by Arthur Whitney of Mendham Township in 1919 and deeded to the borough in 1938 for use as its municipal building.

This east-west roadway is well over 200 years old, and has been called the Washington Turnpike, the Mendham-Morristown Road, and the William Penn Highway at various times in its history.

[52] The district was added to the National Register of Historic Places on April 18, 1985, for its significance in agriculture, commerce, architecture, settlement, and religion from 1750 to 1924.

[53] According to the National Park Service: The Mendham Historic District consists of 140 properties, generally well preserved, that illustrate the history of the village from its eighteenth century founding through its 1906 incorporation as a borough, and into the first third of this century when infill building completed development within the historic bounds of the village.

The District covers the central crossroads of the village, and extends as far as the area nineteenth century maps illustrate as "Mendham, P.O.

The conjunction of religious, residential, and commercial buildings that have established Mendham's village character are well preserved today.

[64] Based on data from the 2006–2010 American Community Survey, the borough had a per-capita income of $51,875, ranked 89th in the state.

[6] The borough form of government used by Mendham Borough is a "weak mayor / strong council" government in which council members act as the legislative body with the mayor presiding at meetings and voting only in the event of a tie.

The mayor can veto ordinances subject to an override by a two-thirds majority vote of the council.

The mayor, presides over the borough council meetings and only votes in order to break a tie.

As of February 2025[update], Republican Neil Sullivan is serving as acting Mayor, temporarily filling a term that expires on December 31, 2026.

[79] In February 2022, the borough council selected Neil Sullivan from a list of three candidates nominated by the Republican municipal committee to fill the seat expiring in December 2022 that had been held by Mary Sue Martin until she resigned from office the previous month.

[80] In January 2019, the borough council appointed James Kelly to fill the term expiring in December 2019 that became vacant when Christine Glassner took office as mayor.

[83][84][85] For the 119th United States Congress, New Jersey's 7th congressional district is represented by Thomas Kean Jr. (R, Westfield).

[134] The high school district's board of education is comprised of nine members who are elected directly by voters to serve three-year terms of office on a staggered basis.

Westmont is dually accredited by the American Montessori Society and the Middle States Association of Colleges and Schools.

[139] Until 2005, Mendham was home to the Assumption College for Sisters, a two-year women's college that is open to lay students as well as those pursuing religious lives, operated by the Sisters of Christian Charity; the school has moved to the Morris Catholic High School campus in Denville Township.

NJ Transit offered service on the MCM4 and MCM5 routes until 2010, when subsidies to the local provider were eliminated as part of budget cuts.