Longmont 155 | Colorado 150 | United States 250 - City of Longmont

Longmont 155 | Colorado 150 | United States 250

Historical photo of Main Street in Longmont CO with an overlaying logo marking the 155-150 and 250 USA anniversaries in 2026.

Celebrating 155 years of Longmont 

 

Did you know 2026 marks not one, not two, but three significant anniversaries?

In 2026, Longmont turns 155, Colorado will celebrate 150 years of Statehood, and the United States will mark 250 years since the signing of the Declaration of Independence. These triplet milestones are a rare and exciting opportunity to unite with our community in celebration of our past and to imagine our future together.

 

In Longmont, we will mark these anniversaries by exploring the history of our city and by hosting commemorative events and activities.

 

Check out the Celebrations Calendar below, invite your friends and family to join in the fun, and follow along as we journey through history and celebrate together!

 

Celebrations Calendar

Independence Weekend Free Concert
Independence Weekend Free Concert
Friday, July 3 • 6 pm - 10 pm
700 Longs Peak Ave. Longmont, CO 80501 United States
Recreation Services
Independence Weekend Festival
Independence Weekend Festival
Saturday, July 4 • 5 pm - 10 pm
110 Emery St Longmont, Colorado 80501 United States
Recreation Services
History Colorado presents Lincoln Hills: Mountain Sanctuary
History Colorado presents Lincoln Hills: Mountain Sanctuary
Wednesday, Aug. 12 • 6:30 pm - 7:30 pm
350 Kimbark Street Longmont, Colorado 80501
Library
View Events

Longmont Legacy

with Erik Mason,
Longmont Museum Director

 

The availability of water has been an essential part of Longmont’s success since its founding in 1871. Irrigation ditches from St. Vrain and Left Hand creeks watered the farm fields around Longmont, allowing farmers to grow vegetables, wheat, and sugar beets in dry Colorado seasons.

 

Following a fire that destroyed many buildings in downtown in 1879, Longmont residents voted to build a pressurized domestic water system. It used underground pipes and a reservoir on Sunset Hill to bring fresh, clean water to Longmont homes starting in 1883. Longmont was also a charter member of the massive Colorado-Big Thompson project, a Federally-funded system of tunnels, dams, and reservoirs that brings water from the Western Slope to the Front Range.

 

In the Spotlight:

Longmont’s Water 

 

  • Black and white print of the Highland Ditch full of water. Photo is taken from center of ditch, following it back. Sides are reinforced with wooden stakes and branches. Ditch is narrow in back with a wooden structure and step leading into a wider area in foreground. Right side is lined with trees. Background is open fields with mountains in distance.
  • Four girls in swim suits and bathing caps sit on sand with a boy in long pants, white shirt, dark belt, and light colored cap standing behind them. In the background is a building with brick colonnades and trees and a dark car parked up against some white fence posts.
  • Black and white photo of Sunset Swimming Pool full of kids. Caption: Pool manager Reggie Batt Jr. Surveys the shallow end of Sunset Swimming Pool Friday in the first day of the regular season of swimming. Batt estimated the crowd in the pool at 700, a few short of the maximum allowable. The pool will remain open until Labor Day with registration for Red Cross swimming lessons being made at the Longmont Recreation Department at 700 Longs Peak Ave. Published in the Times-Call on June 10, 1972.
  • Black and white print of flood on Main St. 1921. Sign on one building reads "Longmont Works" only partly visible. Another sign reads "Motor Cycle Service Station". Main buildings are: Buick (523 Main) Service, Boise Payette Lumber, Motorcycle shop. Terry Lake flood.
  • Color print of Longmont Fire Department fire engine with firefighters on top and driving through flooded streets of Longmont during flood of 2013. On right side of photo is a partial view of people in a boat.

Captions:

 

        1. Highland Ditch irrigates thousands of acres north of Longmont.
        2. Virginia Sullivan and friends sit on the beach in their swimsuits at Sunset Pool in 1929.
        3. Opening day at Sunset Pool, June 10, 1972. (Paul Flanders / Longmont Times-Call)
        4. The 500 block of Main Street during the Terry Lake flood, June 3, 1921 – the “Motor-Cycle Service Station” in the foreground is where Mike O’Shay’s restaurant stands today.
        5. A Longmont Fire Department engine pushes through flooded streets during the September 2013 flood, with residents watching from a boat nearby.

Explore More History with Longmont’s Virtual Tours 

Women of Longmont Virtual Tour

Discover the lives of influential women who helped make Longmont the vibrant, community-focused town it is today.

Historic Downtown Virtual Tour

Enjoy historic photographs, text, and audio recordings that virtually walk you through more than a dozen downtown locations.

Latino History Virtual Tour

This tour explores Longmont’s Latino neighborhoods and heritage while honoring some of the many sacrifices, challenges and successes experienced by this remarkable community.

Is Sesquisemiquincentennial a real word?

logo for Longmont celebration of 155, CO150, USA 250 celebrationsIt sure is! You may see “Sesquisemiquincentennial” used around the state of Colorado this year. In 2026, Colorado celebrates its 150th anniversary of statehood (sesquicentennial) and the United State’s 250th anniversary (semiquincentennial) since the signing of the Declaration of Independence. Learn about more celebrations around the state on the History Colorado website.

 

Sesquicentennial + Semiquincentennial = Sesquisemiquincentennial

 

The City of Longmont, in collaboration with the American 250-Colorado 150 Commission, celebrates this unique anniversary year by looking back at Longmont’s 155 years of history. Follow this webpage to learn more about how you can celebrate with us, in person and online!

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