|Founded||1975, Seattle, Washington, U.S.|
|Headquarters||U.S. Bank Centre
Seattle, Washington, U.S.
|Lance Josal, CEO|
|Services||Architecture; Interior Design; Graphic Design; Strategic Consulting; Real Estate Strategies; Master Planning; Brand Experience|
Number of employees
Callison was an international architecture firm based in Seattle, Washington. Callison was founded by Tony Callison in 1975 and grew to 900 employees around the world prior to its acquisition by Arcadis NV in 2014. In October 2015, Callison was formally merged with another Arcadis subsidiary, RTKL Associates, to form CallisonRTKL headquartered in Baltimore, Maryland.
Callison planned and designed retail, hospitality, mixed-use, workplace, corporate and healthcare projects worldwide.
From its founding in Seattle in 1975, the company grew to over 900 employees worldwide, with offices across the globe: Seattle, Los Angeles, Mexico City, Dallas, Scottsdale, New York City, London, Dubai, Beijing, Shanghai and Guangzhou.
Shortly after the acquisition Arcadis began marketing Callison together with another recent acquisition, Baltimore-based RTKL, with a combined "CallisonRTKL" website and press releases. In October 2015, the two firms were formally merged to form CallisonRTKL headquartered in Baltimore, Maryland. At the time of the merger, the two firms together had together booked $402.4 million in architecture and engineering revenue in the prior year, and Architectural Record ranked the combined firms fifth in the nation.
Callison was ranked in 2008 as the number one retail design firm in the world by Building Design magazine. In 2008, ENR ranked Callison #12 in "The Top 100 Green Design Firms". Callison was awarded "Design Firm of the Year" by DDI for 2008 
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- Inorbit Hyderabad - Hyderabad, India
- Hongyi Plaza - Shanghai, China
- FlatIron Crossing Mall - Broomfield, Colorado
- The Pearl-Qatar – Porto Arabia - Doha, Qatar
- W Hotel - Seattle, Washington
- Unitech Grande - Noida, India
- Harvey Nichols - Dubai and Jakarta
- Boeing World Headquarters - Chicago, Illinois
- 2201 Westlake - Seattle, Washington
- Grand Gateway - Shanghai, China 
- Sogo - Osaka, Japan
- Swedish Medical Center, Eastside Specialty Center - Issaquah, Washington
- Hotel Terra - Jackson Hole, Wyoming
- The Bravern - Bellevue, Washington
- Harrods White Cosmetics Hall - London, England
- St. Charles Medical Center Redmond - Redmond, Oregon
- Microsoft Campus - Redmond, Washington
- Greenbelt 3 - Manila, Philippines
- Lotte Center Hanoi - Hanoi, Vietnam
- Nordstrom - Since 1975 Callison has provided the retailer (both companies are based in Seattle) the design for more than 155 new and remodeled stores; and continues to complete 10 projects, on average, every year for the company.
- Bhatt, Sanjay (20 October 2015). "Callison merges into another architecture firm, HQ shifts to Baltimore". The Seattle Times. Retrieved 8 April 2016.
- Gonzales, Angel (21 August 2014). "Seattle architecture firm Callison bought by Dutch giant". The Seattle Times. Retrieved 26 August 2014.
- Press Release (15 January 2015), "CallisonRTKL Projects Win RDI Awards" http://www.callisonrtkl.com/news/callison-projects-win-rdi-awards/ . Accessed 8 April 2016.
- http://emag.digitalpc.co.uk/cmpi/worldarch08.asp World Architecture 100 (Building Design), 2008
- "Top Green Design Firms 2008', "Engineering News-Record", June 23, 2008.
- "Design Firm of the Year', "Display and Design Ideas", September 2, 2008.[dead link]
- Van Bronkhorst, Eric (June 24, 2013). "The List: Top 5 architecture firms in the Puget Sound area (slide show)". Puget Sound Business Journal. Retrieved February 21, 2016.
- "Callison.com". Callison Website. Callison. Retrieved 7 November 2014.
- Binder, Georges (2006). 101 of the World's Tallest Buildings. Victoria, Australia: The Imaging Publishing Group. pp. 136–137. ISBN 1-86470-173-0.