Mifflinburg is a borough in Union County, located in the Susquehanna River Valley of central Pennsylvania, United States. In 1792, Mifflinburg was settled by Elias and Catharina Youngman and 8 other families, many of them German, and the village of Mifflinsburgh (now Mifflinburg) was formed. It was named for Thomas Mifflin, who was governor of Pennsylvania and first governor under the PA Constitution of 1790, and a signer of the U.S. Constitution. Youngmanstown was another name based upon common nemonclature only, but not officially. In 1827, Mifflinburg, a.k.a. Youngmanstown, and another town adjacent to the east named Greenville, a.k.a. Rhodestown, (common nemoncloture), were combined and incorporated into a borough. The first horse drawn buggy and carriage manufacturing company was established in 1845; and Mifflinburg would become the Buggy and carriage manufacturing capital of the United States in the late 19th century. There are many Victorian homes and downtown business buildings. Mifflinburg is known for The Mifflinburg Buggy Museum, Buggy Day, annual authentic Christkindle Market the second weekend of December, and German Oktoberfest.

As of the 2010 census, there were 3,540 people, 1,506 households, and 1,028 families living in the borough. The population density was 1,976.0 inhabitants per square mile (762.9/km). There were 1,605 housing units at an average density of 882.4 per square mile (340.7/km). As of 2010, the racial makeup of the borough was 97.5% White alone, 0.9% Hispanic, 0.6% Black alone, 0.5% two or more races, 0.3% Asian alone, 0.08% Hawaiian or Pacific Islander alone, 0.06% other race alone, and 0.03% American Indian alone.

Major tourist attractions include

• Mifflinburg Buggy Museum, which celebrates the era (circa 1880 - 1915) when Mifflinburg was known as "Buggytown, USA" due to its reputation as a major manufacturer of quality horse-drawn carriages and sleighs
• Annual "Christkindl Market" (a traditional German Christmas festival).

The borough is situated on lands that were originally granted in 1769 to the veteran officers who served under Colonel Henry Bouquet during Pontiac's War (1763-1766) in lieu of payment for their service and ultimate victory at the Battle of Bushy Run in defense of Fort Pitt (Pittsburgh). In 1782 or 1783, Elias and Catharina Jungman (Youngman) and their children, came from Fort Augusta (now Sunbury) Pennsylvania to the Buffalo Valley with 8 other families to settle on land purchased by Elias from Catharina's father, George Nagle. In the summer of 1792, Elias surveyed and divided the land into 60' by 120' plots that were sold to other adventurous settlers, many of them German, and the village of Mifflinburg was formed (common nomenclature was attributed to the town being named "Youngmanstown", as was historically the case, but was Mifflinburg in the deeds as early as 1792). In 1797, George Rote (Rhoade) laid out a village just east of Youngmanstown, known as Greenville or Rotestown (common nomenclature). Eventually, the two settlements joined at Third Street. In 1827, the two villages combined and were incorporated. The combined village was named Mifflinburg, in honor of Thomas Mifflin, the first Governor of Pennsylvania after the 1790 Constitution. The merged towns were known as Mifflinburg before 1827 however, because when Union County was formed from Northumberland County on March 22, 1813, that PA legislative act also established Mifflinburg as the seat of government of the newly formed county, with the first courthouse located at 406 Green Street and other government offices located in various other buildings throughout the town. It remained the county seat until 1815 when it was moved to New Berlin, and then to Lewisburg in 1855 where it remains today.

In 1845, George Swentzel set up Mifflinburg's first buggy business. Soon other buggy manufacturers set up their own shops in Mifflinburg, and by 1855, with a population of 800, Mifflinburg hosted thirteen coachmakers. By the 1880s, with more than fifty buggy and sleigh factories, Mifflinburg became known as “Buggy Town” because its buggy makers produced more horse-drawn vehicles per capita than any other town in the state.

The Mifflinburg Historic District, Hassenplug Bridge, and William A. Heiss House and Buggy Shop are listed on the National Register of Historic Places.

Mifflinburg is located at 40°55′8″N 77°2′48″W / 40.91889°N 77.04667°W / 40.91889; -77.04667 (40.918939, -77.046800), approximately 25 miles (40 km) southwest of Williamsport.

According to the United States Census Bureau, the borough has a total area of 1.8 square miles (4.7 km), all land.

Historical population

Census	Pop.	Note	%±
1850	783		—
1860	865		10.5%
1870	911		5.3%
1880	1,168		28.2%
1890	1,417		21.3%
1900	1,436		1.3%
1910	1,559		8.6%
1920	1,744		11.9%
1930	1,959		12.3%
1940	2,090		6.7%
1950	2,259		8.1%
1960	2,476		9.6%
1970	2,607		5.3%
1980	3,151		20.9%
1990	3,480		10.4%
2000	3,594		3.3%
2010	3,540		−1.5%
2020	3,424		−3.3%
2021 (est.)	3,404		−0.6%
Sources:

As of the census of 2000, there were 3,594 people, 1,506 households, and 1,028 families living in the borough. The population density was 1,976.0 inhabitants per square mile (762.9/km). There were 1,605 housing units at an average density of 882.4 per square mile (340.7/km). As of 2010, the racial makeup of the borough was 97.5% White alone, 0.9% Hispanic, 0.6% Black alone, 0.5% two or more races, 0.3% Asian alone, 0.08% Hawaiian or Pacific Islander alone, 0.06% other race alone, and 0.03% American Indian alone.

There were 1,506 households, out of which 32.1% had children under the age of 18 living with them, 55.5% were married couples living together, 9.6% had a female householder with no husband present, and 31.7% were non-families. 27.7% of all households were made up of individuals, and 13.7% had someone living alone who was 65 years of age or older. The average household size was 2.39 and the average family size was 2.91.

In the borough the population was spread out, with 25.3% under the age of 18, 7.6% from 18 to 24, 28.6% from 25 to 44, 21.9% from 45 to 64, and 16.6% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 87.4 males. For every 100 females age 18 and over, there were 85.5 males.

The median income for a household in the borough was $34,906, and the median income for a family was $43,520. Males had a median income of $30,568 versus $21,315 for females. The per capita income for the borough was $17,161. About 7.6% of families and 9.9% of the population were below the poverty line, including 13.7% of those under age 18 and 8.7% of those age 65 or over.

Major employers include Weis Markets (a supermarket), Mifflinburg Area School District, CVS, Cole's Hardware, Ritz-Craft (a manufacturer of modular homes), and Yorktowne (a cabinetry manufacturer). In 2005, Yorktowne management made the decision to move most of the Mifflinburg operations to Danville, Virginia, rather than comply with new air pollution regulations in Pennsylvania.

Major tourist attractions include

• Mifflinburg Buggy Museum, which celebrates the era (circa 1880 - 1915) when Mifflinburg was known as "Buggytown, USA" due to its reputation as a major manufacturer of quality horse-drawn carriages and sleighs
• "Christkindl Market" (annual German Christmas festival)

Mifflinburg's business district is centered on Pennsylvania Route 45.
U.S. Route 15, the primary north/south highway through central Pennsylvania, is located nine miles to the east.
The most direct route to the nearest interstate highway exit involves going over Sand Mountain on an unpaved road to reach Interstate 80, exit 192. Most westbound drivers will opt for exit 185 instead, while eastbound drivers will use exit 210.

A Fullington Trailways station is located nine miles east.

Mifflinburg was once served by the Lewisburg and Tyrone Railroad. Today, the closest passenger rail access is the Lewistown Amtrak station.

Although Williamsport Regional Airport (IATA: IPT) is the closest airport with scheduled airline service, travelers often seek out the lower fares at Trenton–Mercer Airport (IATA: TTN), Philadelphia International Airport (IATA: PHL), or Washington Dulles International Airport (IATA: IAD).
The general-aviation Penn Valley Airport (IATA: SEG) is located 15 miles southeast.

• Official website
• Mifflinburg Area School District
• Mifflinburg Heritage & Revitalization Assoc.
• Profile of Union County, PA
• History of the Mifflinburg Body Company