Mon-Thurs 8AM-5PM , Fri 8AM-2PM  |  605-342-5630  |  810 Quincy Street Rapid City, SD 57701

About Us


Ketel Thorstenson, LLP (KTLLP) has been operating as an accounting practice in Rapid City in one form or another since 1936 when Harold Heims first opened the practice and hired A.C. (Bud) Thorstenson shortly after. The firm started in offices above the old North Western Warehouse and then moved to space above Staple & Spice. The building at the current 810 Quincy Street address was constructed in 1966; the same year that Roy Ketel and Rich Siekman worked together to form a new partnership.


The rich history of change and growth has led to three name changes and seven building remodels/additions. In addition to growing the practice, the Partners of KTLLP continue to be visionaries and delve into business solutions for their clients outside of traditional accounting services.


Today the KTLLP family employs over 130 professional staff members, including 18 partners, and operates out of Rapid City, Spearfish, and Custer, SD, and Gillette, WY. We are proud of our longevity and thankful for all of the clients who we consider as friends. KTLLP looks forward to many more years of continued growth serving the regional market.


To inspire excellence in our people, clients, and communities by building meaningful relationships through progressive thinking, collaboration, and passion.

Core Values



Provide exceptional and accurate professional services delivering premium value and exceeding expectations

Innovation happens through teamwork and shared goals



Offer knowledgeable teams dedicated to delivering strategic solutions to ensure our people, our clients, and our communities reach their fullest potential

Achive excellence through teamwork.



Foster our strong foundation of being a dependable, honest, and accountable resource generating continued trust

Being our true selves promotes trust and creates new friendships



Nurture a supportive environment promoting genuine interest, giving back, growth, and success

Making time to connect and discuss varied thoughts and ideas



Encourage diverse thoughts and opinions through collaboration while delivering a variety of services and creating strategic relationships


-Total Years-

In Business


-Years Combined-

Partner Group Experience


-Eggs Eaten-

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On Staff


-Tax Returns-

Prepared Yearly


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During Tax Season

Rapid City

(605) 342-5630
810 Quincy Street
Rapid City, SD 57701
Fax: (605) 342-2172


(605) 642-7676
123 E. Jackson Blvd Suite 2
Spearfish, SD 57783
Fax: (605) 642-2616


(605) 673-3220
609 Mt. Rushmore Road
Custer, SD 57730
Fax: (605) 673-3220


(307) 685-4433
305 S. Garner Lake Rd Suite A
Gillette, WY 82718
Fax: (307) 682-6321



Harold Heim moves from New York and starts an accounting practice in Rapid City


S.S. Schouweiler moves to Rapid City and starts accounting practice Dale Sayler starts working for Heim


A.C. (Bud) Thorstenson starts working for Heim S.S. Schouweiler buys the Heim Practice. Thorstenson and Sayler work for him


The Firm of Schouweiler, Sayler & Thorstenson is formed


Sayler, Thorstenson, Jerry Benson, Roy Ketel and Rich Siekman form a new partnership called Sayler, Thorstenson & Co


IBM System 1130 computer installed


Addition constructed to house computer room and additional offices


Acquire property adjoining 810 Quincy in Rapid City


Addition to 810 Quincy constructed


John Walker and Dennis Nelles admitted as partners Office opened in Spearfish


Dale Sayler withdraws from partnership. Roy Ketel becomes the first Managing Partner Firm becomes a subscriber of Grant Thornton Accounting & Auditing Materials


First PC Computer put in service. Pete Bergman and Mike Finnegan admitted as partners


Firm has first peer review by AICPA team


Dan Corey practice purchased and employed. Black Monday stock market crash. AICPA celebrates its 100th Anniversary


Firm changes name to Ketel Thorstenson, LLP. Merger with Vigoren and Stokes in Spearfish. Rex Vigoren becomes partner


Paul Thorstenson, Kay Walker and Donna Denker admitted as partners


Addition to 810 Quincy constructed


First tax return is e-filed


Addition to 810 Quincy completed. Business Valuation department established. Building and parking at 823 Quincy purchased


Tax practice of J&J Bookkeeping in Custer purchased. All personnel employed


Dave Hoyer joins Firm. Practice of Herb Kaden acquired


John Walker becomes new Managing Partner. Steve Schacht and Brent Siekman admitted as partners. KT Connections, Inc., a computer and telecommunications firm organized


Building at 829 Quincy purchased and remodeled for KT Connections Inc.


Denise Webster and Merle Karen admitted as partners


Acquisition of McGladrey & Pullen/RSM McGladrey. Jean Smith, Clark Kraemer, Fred Krush and Craig Steinman admitted as partners. Dakota Backup & Recovery, a data backup and disaster recovery solution provider organized


Joel DeVries admitted as partner


New building addition officially opens for business


Nina Braun, Doug Kenoyer and Jennifer Konvalin admitted as partners


KTLLP Executive Committee organized to manage the firm. Denise Webster was appointed as COO, John Walker as CFO and Paul Thorstenson as CEO


Kevin Sickels admitted as partner. Merger with Rustad Furseth in Williston, ND


Jeff Maine practice purchased and employed


Fred Krush retires from Ketel Thorstenson, LLP. Traci Hanson admitted as partner


Ketel Thorstenson, LLP celebrates 80 years in business


Pete Bergman retires from KTLLP. Michelle Minnerath admitted as partner


Steve Schacht named CFO. John Walker retires from KTLLP. Merger with Todd Hoese, CPA, LLC in Gillette, WY. Todd Hoese is admitted as partner


Jess Weaver and Jackie Maguire admitted as partners

Community Involvement

At Ketel Thorstenson, LLP social responsibility is ingrained in our core values. We know that strong companies build strong communities. KTLLP’s community involvement supports various regional organizations as club members, officers, sponsors, donors, and volunteers.

Whether it’s the arts, education, health-related issues, supporting kids and families, special interest groups or non-profits, KTLLP makes ongoing efforts to contribute its time, talents and resources to the greater Black Hills area community including Rapid City, Custer, Spearfish, and Gillette.


KTLLP staff are active many different civic organizations, including but not limited to:
  • Elevate Rapid City
  • Rapid City Area Chamber of Commerce
  • Spearfish Chamber of Commerce
  • Custer Area Chamber of Commerce
  • Salvation Army
  • Destination Rapid City
  • Rapid City Downtown Kiwanis
  • Rapid City Cosmopolitan Club
  • Zonta Club of the Black Hills
  • Zonta Club of the Northern Hills
  • Zonta Club of the Southern Hills
  • Rotary Club of Rapid City
  • Young Professionals Group
  • Leadership Rapid City
  • South Dakota Center for Enterprise Opportunity (SD CEO)


KTLLP staff volunteer their time and talents as well as make donations to many worthy organizations in the Black Hills.
  • United Way of the Black Hills and the “Day of Caring”
  • Black Hills Federal Credit Union School Supply Drive
  • Friday “Jeans Days”
  • YMCA of Rapid City
  • United Blood Services
  • Tough Enough to Wear Pink
  • Feeding SD
  • The Hope Center
  • Club for Boys Free Throw Challenge and Holiday Gift Wrapping
  • Downtown Rapid City
  • Summer Nights
  • Movies Under the Stars
  • Youth and Family Services and Kids’ Fair
  • Storybook Island
  • SD Special Olympics Polar Plunge
  • Junior Achievement
  • Harney Little League
  • Canyon Lake Little League
  • Timberline Little League


KTLLP plays an additional role by assisting in sponsorship. Below are just some of the organizations and events we sponsor.
  • The Central States Fair
  • Black Hills Stock Show
  • Black Hills Works Gala
  • CASA Fire and Ice Gala
  • Children’s Home Society Golf Tournament
  • Custer Area Chamber of Commerce
  • Day of Excellence
  • Feeding SD Hungry Bowls
  • Rapid City Area Chamber of Commerce
  • Young Professionals Group
  • Networking’s Not Natural
  • Relay for Life
  • South Dakota Center for Enterprise Opportunity (SD CEO)
  • YFS Denim and Diamonds
  • Wellfully Stampede
  • Homeless But Not Hopeless Golf Tournament
  • Women in Science
  • The Burning Beetle
  • Innovation Expo
  • Black Hills Area Council Leadership Breakfast


Jeans Days Annually

One way KTLLP supports local organizations is with a fun donation opportunity which allows staff to wear jeans to work in exchange for a donation. Participation is optional but many staff gets involved because it is a quick and easy way to make an immediate impact on our community.


Organizations Supported
There are so many wonderful organizations and non-profits in the greater Black Hills area with missions of meeting the variety of needs in our community. KTLLP is passionate about helping as many people as we can.


Volunteer Hours Annually
KTLLP is driven to serve the greater Black Hills community, where we live and work. Because of this community involvement dedication, KTLLP gives each employee general public service hours annually to use toward the causes and organizations that they are passionate about.

online payments

If you would like to pay an invoice online with a credit card click on the Pay Now button.  Pay_Now_button

You also have the option to pay your invoice electronically via ACH (bank to bank transfer) at no cost to you by completing the ACH form and returning it to your accountant.


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