Despite being just the 23rd most populous city in Montana, Glasgow is the most populous city for over 110 mi (177 km), thus making it an important economic hub for a large region in Eastern Montana. Both Amtrak and the National Weather Service operate facilities in Glasgow that link the city to the surrounding region.

Native Americans inhabited the region for centuries, and extensive buffalo and pronghorn antelope herds provided ample food for the nomadic tribes. The Nakoda, Lakota, and Dakota peoples alternately inhabited and claimed the region from the 16th to the late 19th centuries. In 1804 the Lewis and Clark Expedition came within 15 miles (24 km) of the future site of Glasgow and noted the extensive herds of buffalo and various game. In 1851, the US government formed the first treaty with the Native American tribes, in 1885 the tribes engaged in the last known buffalo hunt in the region.

From 1885 to Montana Statehood in 1889, the tribes participated in agreements with the US government to re-drawing the Fort Peck reservation boundaries in exchange for federal subsidies. As more and more homesteaders moved into the surrounding areas, pressure was placed on Congress to open up the Fort Peck Reservation to homesteading, resulting in tribes leaving the Glasgow area.

Glasgow was founded in 1887 as a railroad town by James Hill, who was responsible for creating many communities along the Hi-Line. He and a local railroader named the town when they spun a globe with a finger landing on Glasgow, Scotland. Glasgow grew during the 1930s when President Franklin D. Roosevelt authorized the construction of the Fort Peck Dam, which became a major source of employment for the Glasgow area.

During World War II, the Glasgow Army Airfield housed the 96th Bombardment Squadron and 614th Bombardment Squadron, flying B-17 Flying Fortresses, at different times during the war. Starting in December 1944, a German POW camp was established at the facility, lasting until the end of the war. After the war ended the base was closed, and part of the facility eventually became the present day Glasgow Valley County Airport. Glasgow was the death place of Lieutenant Colonel Ronald Speirs, famed member of Easy Company, 101st Airborne.

In the 1960s, the population rose to about 6,400 due to the nearby presence of the Glasgow Air Force Base, (SAC air command and housing B-52 bombers) used during the Vietnam War and the earlier part of the Cold War. A significant amount of mid-century modern and Googie-style architecture was built then. After the de-activation and closure of the base in 1969, Glasgow's population declined to about half its one-time size by 1990, when the loss rate stabilized. Glasgow still functions as the major regional administrative, shopping and services hub for Valley County and some of the areas beyond.

According to the United States Census Bureau, the city has a total area of 1.43 square miles (3.7 km), all land. The town has an elevation of 2,093 feet (638 m). It is nestled in the Milk River Valley with the river itself meandering along to south.

Glasgow is 18 miles (29 km) west of Fort Peck Lake, the fifth largest artificial lake in the United States. The lake is popular for fishing and for recreation. The Charles M. Russell National Wildlife Refuge surrounds the lake providing an opportunity to experience nearly the same surroundings as encountered by the Lewis and Clark Expedition in 1805.

Using data from Oxford University's Big Data Institute, The Washington Post, in 2018, identified Glasgow as "the middle of nowhere" for the contiguous United States. The article stated "Of all towns with more than 1,000 residents, Glasgow ... is farthest – about 4.5 hours in any direction – from any metropolitan area of more than 75,000 people".

Glasgow experiences a continental semi-arid climate (Köppen climate classification BSk) with long, dry winters with typically freezing but exceedingly variable temperatures and hot, dry summers. The extreme variability of winter temperatures is due to the large warming produced by chinook winds as air descending from the Rockies is warmed, contrasting with very cold continental air masses typical of inland locations at this latitude. As an illustration, the record cold month of February 1936 averaged −15.8 °F (−26.6 °C), but the two warmest Februaries of 1931 and 1984 averaged above 32 °F or 0 °C and had mean maxima above 43.5 °F or 6.4 °C. Snowfall averages 34.8 inches or 0.88 metres per year. Tornadoes are a rare occurrence. Two F2 tornadoes did, however, hit the Glasgow area on June 25, 1975.

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As of the 2010 census, there were 3,250 people, 1,479 households, and 834 families residing in the city. The population density was 2,272.7 inhabitants per square mile (877.5/km). There were 1,653 housing units at an average density of 1,155.9 per square mile (446.3/km). The racial makeup of the city was 91.8% white, .2% African American, 4.5% Native American, .3% Asian, .4% from other races, and 2.7% from two or more races. Hispanic or Latino of any race were 1.8% of the population.

There were 1,479 households, of which 26.6% had children under the age of 18 living with them, 43.5% were married couples living together, 9.1% had a female householder with no husband present, 3.8% had a male householder with no wife present, and 43.6% were non-families. 39.7% of all households were made up of individuals, and 19.6% had someone living alone who was 65 years of age or older. The average household size was 2.13 and the average family size was 2.85.

The median age in the city was 45.6 years. 22.7% of residents were under the age of 18; 5.2% were between the ages of 18 and 24; 21.3% were from 25 to 44; 28% were from 45 to 64; and 22.7% were 65 years of age or older. The gender makeup of the city was 47.8% male and 52.2% female.

The median income for a household in the city was $35,504. 14.5% of the population were below the federal poverty line, compared to 15.1% for the USA as a whole.

In May 2012, the major industries present in Glasgow were retail (23% of employment), public administration (16%), construction (14%), and health care and social assistance (7%). Farmers and farm services comprised 4% of employment. As of June 2014, the unemployment rate was 3.2%.

For Valley County, the median value of owner-occupied housing units was $160,800 from 2017 to 2021.

Glasgow is served by the Glasgow School District with three public schools. For the 2021–2022 school year, 379 students were enrolled in kindergarten through 5th grade at Irle Elementary School. At Glasgow Middle School, for 6th–8th grade, 167 students were enrolled. Glasgow High School had 245 students enrolled. The team name for the school is the Scotties.

From 2017–2022 census data on those 25 years and older in Valley County, 93% had attained high school graduation or higher, 19.1% had a Bachelor's degree or higher.

Glasgow City-County Library serves the area.

As of 2023, the Scotties of Glasgow High School have won 48 Montana state championships. Glasgow High School offered 13 sports in 2023. Since the 1992–93 school year, they have competed as a Class B school, a designation used by the Montana High School Association based on population.

They have won 14 state championships and 33 state trophies in boys wrestling. The Girls Cross Country team has won the state championship 16 times.

The Glasgow Reds baseball team competes in the American Legion Baseball league, played by 13-to-19-year-olds. They finished second at the state championships in 2000 and 2012 and third in 1999, 2013, and 2015.

There were no reports of rape or murder occurring in Glasgow in 2010, compared with one murder the previous year, and 16 incidents of rape from 2003 to 2008. Overall, the crime rate to 2010 appears to be in a general downward trend, and is well below the national average.

A sheriff's detention facility was completed in April 2011 at a cost of $3.16 million. The facility, located downtown, is 10,000 square feet (930 m) and has 26 beds, replacing the 16 beds of the previous jail. The detention center houses inmates from local police and sheriff, as well as regional inmates for agencies such as the FBI, U.S. Marshals Service and Montana Highway Patrol and has an average of 16 inmates on any given day.

Glasgow is on the Hi-Line of the BNSF Railway and is served daily westbound and eastbound by Amtrak's Empire Builder route.

Glasgow is served by Glasgow Valley County Airport and has daily commercial service to Billings. Since 2013, the commercial air service provider is Cape Air.

Glasgow and the greater Valley County region are served by a non-profit taxi/bus service called Valley Country Transit. Bus and/or Van rides are available daily for in-county travel and one-way or two-way trips out of the county. Riders are charged on a per trip basis and must call in a ride. As of 2022, the transportation service, Uber is also now in operation within city limits.

Glasgow is located on U.S. Highway 2, which is a major east-west traffic corridor of the northern Great Plains region. Montana Highway 24 passes nearby the city, a major north-south route connecting southern Montana to Canada. No Interstates run near the region.

Glasgow is part of the Glendive Media Market, as of 2021, the smallest tracked by Neilson serving an estimated 3,900 homes.

• The Glasgow Courier, established in 1913 and published every Wednesday, is the newspaper of record for Valley County,
• The BS Buzz, is a daily newspaper published by BS Central Inc. The Buzz offers advertising options on daily, weekly and monthly rates.

• KLTZ, 1240 AM
• KLAN, 93.5 FM

• K18BN-D (18.1 PBJ) UHF 18

• Stacy Edwards, actress
• Julie Golob, professional sharpshooter and competition shooter
• Ann Hould-Ward, Tony-winning costume designer
• Michael McFaul, former United States Ambassador to Russia
• Donald Grant Nutter, 15th governor of Montana
• Tony Raines, NASCAR driver
• Uan Rasey, trumpeter who played on several motion picture soundtracks in the 1950s and 1960s
• Steve Reeves, bodybuilder and actor
• Daanyaal Hussain, Race car driver for the now defunct Talbot
• Jerry Rosholt, journalist and author
• Brian Salonen, NFL player
• Anthony Washington, three-time Olympic discus thrower

Wikivoyage has a travel guide for Glasgow (Montana).

Wikimedia Commons has media related to Glasgow, Montana.

• Official website
• Glasgow Area Chamber of Commerce
• Two Rivers Economic Growth