The community, 40 miles (64 km) west of New York City, began as a summer getaway for the wealthy in NYC who primarily sought access to the lake.

An amusement park, called "Bertrand's Island", sprang up and was accessible via the lake, trolley or by car through Mount Arlington.

The construction of Interstate 80, a highway that stretches from Teaneck, New Jersey, all the way across the country to San Francisco, California, triggered rapid growth in New York City's suburbs and led to Hopatcong becoming a permanent residential community.

[23][24] During the 1830s, the name of the community had been modified to "Brooklyn", to match the spelling of the city on New York's Long Island.

[25] Hopatcong was originally established as the Town of Brooklyn on April 2, 1898, from portions of Byram Township.

[26] In 1922, residents of Byram Cove, Northwood, and other areas to the west of the original land area of the borough, voted to leave Byram Township and join Hopatcong, leaving the Borough with its current borders.

[27] While the origin of the borough's name is unclear, it is said to derive from Native American phrases variously meaning "stone over water" or "pipestone", among other variations.

[7] The borough form of government used by Hopatcong 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.

[43][44] As of 2024[update], the mayor of Hopatcong Borough is Republican Marie Galate, whose term of office ends December 31, 2027.

[3][45][46][47][48] In December 2016, the borough council chose Michael Francis from three candidates nominated by the Republican municipal committee to fill the seat expiring in December 2019 that had been held by Sylvia Petillo until she resigned from office the previous month in advance of taking a seat on the Sussex County Board of Chosen Freeholders; Francis will serve on an interim basis until the November 2017 general election, when voters will choose a candidate to serve the balance of the term of office.

[49] In turn, Bradley Hoferkamp was chosen to fill the council seat vacated by Francis, including the three-year term that Francis had won in November 2016; Hoferkamp will also serve until November 2017, when the balance of the term will be filled by a candidate selected by voters.

[50] In May 2014, the borough council appointed Frank Padula to fill the vacancy of Richard Hoer, who had resigned the previous month.

[51] Padula served on an interim basis until the November 2014 general election, when he ran unopposed and won the balance of the term of office expiring in December 2016.

[55][56][57] Prior to the 2010 Census, Hopatcong had been part of the 5th Congressional District; the change was made by the New Jersey Redistricting Commission and took effect in January 2013, based on the results of the November 2012 general elections.

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

[72] Among the borough's 2010 Census population, 63.1% (vs. 65.8% in Sussex County) were registered to vote, including 81.3% of those ages 18 and over (vs. 86.5% countywide).

Hopatcong is also known for its yearly "Hopatcong Days" that offer a weekend of events that include a parade, and an array of festivities in Modick Park, sponsored by the local Business Association and including an annual Soap Box Derby and Car Show.