There are five areas that are protected by the Central Pennsylvania Conservancy and 59 natural heritage sites in the county.

More settlers arrived in the 1750s and 1760s and the first gristmill on the western side of the Juniata River was built in the county in 1767.

A public road was built in the county between Tuscarora Creek and a location near Shade Mountain in 1768.

John Hamilton constructed a sawmill and gristmill on Cocolamus Creek in Delaware Township in 1776.

The Dimmsville Covered Bridge in Greenwood Township had been designated as a historic place, but fell into disrepair and collapsed in April 2017.

[3] Juniata County is one of the 423 counties served by the Appalachian Regional Commission,[10] and it is identified as part of the "Midlands" by Colin Woodard in his book American Nations: A History of the Eleven Rival Regional Cultures of North America.

[4] 112,000 acres, or 45% of Juniata County's area is in the Tuscarora Creek watershed, including the borough of Port Royal.

[12] Juniata has a humid continental climate, which is hot-summer (Dfa), except in higher areas where it is warm-summer (Dfb).

[22] In 2000, 45.4% of the population of Juniata County were of German, 20.2% American, 5.7% Irish and 5.0% English ancestry according to Census 2000.

Greenwood Township has the third lowest population density of any administrative division in Juniata County: 27.9 people per square mile.

5.6% had an occupation in the field of education, and a similar number worked in finance, insurance, and real estate.

Mifflin has the highest percentage of houses with full plumbing facilities of any township or borough in the county (100%).

[13] There are six public sewer companies in the county, the largest of which, the Twin Boroughs Sanitary Authority, is used at a rate of 450,000 gallons per day.

[30] The daily traffic of Juniata County's arterial roads ranges from several dozen to several thousand vehicles per day.

The least-trafficked major rural connector road is State Route 2026, which is used by 350 vehicles per day and the most-trafficked major rural connector road is Pennsylvania Route 35, which gets up to 7100 vehicles per day.

[30] There are 254 state-owned bridges in Juniata County, of which 77 are considered structurally deficient by the Pennsylvania Department of Transportation.

The second-longest bridge in the county crosses the Juniata River at Thompsontown Station and is 808.1 feet (246.3 m) long.

[31] For air travel, Juniata County is served by the privately owned Mifflintown Airport and the Stottle Memorial Heliport in Tuscarora Township.

Spruce Hill Township has the lowest percentage of people without a high school diploma (18.00%).

The Juniata County Natural Heritage Inventory considers it to be an "exceptional significance" site.

[33] There are four sites on Tuscarora Creek and its tributaries on the "exceptional significance" list in the Juniata County Natural Heritage Inventory.

It contains a silver maple floodplain forest and is home to Ranunculus flabellaris and many species that are rare in Pennsylvania.

The creek's valley downstream of Pennybaker Island in Lack Township is home to Samolus parviflorus and Quercus shumardii.

It is listed as an "exceptional significance" site on the Juniata County Natural Heritage Inventory and contains a red cedar–redbud shrubland community, which is rare in Pennsylvania.

It is located in Fayette Township and contains a side-oats grama calcareous grassland, which is described as a "very important" natural feature.

The Westfall Prairie is also located in Fayette Township and is home to a number of rare species.

[33] Allegheny Woodrats live on the slopes of the Lewistown Narrows in Milford Township, Juniata County and Northern Myotis bats feed there.

The Lewistown Narrows are an "exceptional significance" site according to the Juniata County Natural Heritage Inventory.

[33] Under Pennsylvania law, there are four types of incorporated municipalities: cities, boroughs, townships, and, in at most two cases, towns.

Boroughs in Juniata County include:[34] Townships in Juniata County include:[34] Census-designated places are geographical areas designated by the U.S. Census Bureau for the purposes of compiling demographic data.