The National Institute of Standards and Technology (NIST) is headquartered in Gaithersburg directly west of I-270.

[N 1] Other major employers in the city include IBM, Lockheed Martin Information Systems and Global Services business area headquarters, AstraZeneca.

Gaithersburg is also the location of the garrison of the United States Army Reserve Legal Command.

[11][12] In 2023, Wallethub announced that Gaithersburg was back in the number one spot for diversity in the U.S.[13] Gaithersburg was settled in 1765 as a small agricultural settlement known as Log Town near the present day Summit Hall on Ralph Crabb's 1725 land grant "Deer Park".

[14] The northern portion of the land grant was purchased by Henry Brookes, and he built his brick home "Montpelier" there, starting first with a log cabin in 1780/3.

This 1,000-acre tract became part of the landmark IBM Headquarters complex built on the then-new I-270 Interstate "Industrial", now "Technology", Corridor in the late 1960s to the 1970s.

[16] The Forest Oak Post Office, named for a large tree in the town, was located in Gaither's store in 1851.

On July 10, 1864, using the route of present-day 355, over 10,000 Confederate troops camped overnight in the area, including the present Bohrer Park, after a one-day march from Frederick after the Battle of Monocacy.

When the railroad was built through town in 1873, the new station was called Gaithersburg, an officially recognized name for the community for the first time.

Gaithersburg boomed during the late 19th century and churches, schools, a mill, grain elevators, stores, and hotels were built.

[16] In 1899, Gaithersburg was selected as one of six global locations for the construction of an International Latitude Observatory as part of a project to measure the Earth's wobble on its polar axis.

The observatory and five others in Japan, Italy, Russia, and the United States gathered information that is still used by scientists today, along with information from satellites, to determine polar motion; the size, shape, and physical properties of the earth; and to aid the space program through the precise navigational patterns of orbiting satellites.

As the population grew, with homes spreading throughout the area, Gaithersburg began taking on a suburban and semi-urban feel, leaving its farming roots behind.

[19] On July 16, 2010, Gaithersburg was part of the area where a 3.6 magnitude earthquake was felt, one of the strongest to occur in Maryland.

After years of decline and loss of tenants, including three of its four anchor stores in 2019, Lakeforest Mall closed on March 31, 2023,[20] with plans to demolish it and redevelop the area.

I-370 is a short spur, starting just west of I-270 in Gaithersburg and heading east to its junction with Maryland Route 200.

Gaithersburg is connected to the Washington Metro via Shady Grove station, which is located just outside the city limits and is the north-western terminus of the Red Line.

Maryland's MARC system operates commuter rail services connecting Gaithersburg to Washington, D.C., with two stations in the city, at Old Town Gaithersburg and Metropolitan Grove, and a third station — Washington Grove — just outside city limits.