810 Quincy Street | Rapid City, SD 57701
(605) 342-5630
(605) 342-2172
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"Far and away the best prize that life offers is the
chance to work hard at work worth doing."

~ Theodore Roosevelt

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Join Our Team

KTLLP – a great place to work

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Friends for Life

Taking time to get to know you

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Trust the Experts

Serving the Black Hills and beyond since 1936

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Have Questions?

We have answers


Ketel Thorstenson, LLP (KTLLP) is celebrating 80 years of serving the Black Hills region. As a leading accounting firm, KTLLP continually looks for ways to innovate and educate for the benefit of our clients. Our clients are our focus. We take the time to get know you and your business. Our mantra is Friends for Life and we live it daily.

Do Your Numbers Add Up?

What are your numbers? Do you know your numbers?
13 –  # of hours an average person spends on preparing their tax return
24 –  # of hours the average business spends on preparing its tax return
74,608 –  # of pages to explain the U.S. tax code
80 –  # of years Ketel Thorstenson, LLP has been business.
Save time and energy! Trust the experts.
Ketel Thorstenson will get your numbers right!


  • Educated. Our staff hold Bachelor’s and Master’s level degrees in Accounting and related fields from accredited institutions.
  • Certified. The American Institute of Certified Public Accountants (AICPA) protects public interest by licensing only the most qualified, experienced, and ethical accountants as CPAs.
  • Ongoing Education. Our team receives advanced training all year long to stay on the forefront of the industry.
  • Expertise. With over 50 CPAs on staff and the combined years of service in the hundreds, our team has the answers to your questions.
  • Professional. Our strong reputation has been built over eight decades of delivering professional service.
  • Partners & Friends. Your CPA knows your name, understands your business, and considers your mutual relationship a partnership; oftentimes, a friendship. This is what we mean by Friends for Life.





810 Quincy Street
Rapid City, SD 57701

(605) 342-5630

(605) 342-2172


123 E. Jackson Blvd.
Suite 2
Spearfish, SD 57783

(605) 642-7676

(605) 642-2616


609 Mt. Rushmore Rd.
Custer, SD 57730

(605) 673-3220

(605) 673-3114


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PO Box 608
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(701) 774-3836

(701) 774-0672