ELO Prof LLC origins run deep in the city of Mitchell, SD and surrounding area. Formerly Endorf, Lurken, Olson & Co, the firm traces its roots to Donald Wohlenberg, a CPA who began practice in Mitchell, SD in the early 1950’s.   Eventually Don merged his practice into a new firm Wohlenberg Gage & Co in 1971. Gary Endorf joined Wohlenberg Gage & Co in 1971 and became a partner in 1973 under the mentorship of Don Wohlenberg. Wohlenberg Gage & Co acquired the practice of Jerry Ross, PA in 1974—many existing relationships can trace their accounting services back to Wohlenberg or Ross. Wohlenberg Gage & Co disbanded in 1982 when the seven offices became individual practices. Gary Endorf reorganized the Mitchell office in October 1982 and Bill Lurken and Dave Olson joined the new partnership of Endorf, Lurken, Olson & Co.  

In October, 1982, the professional union of Endorf, Lurken, Olson & Co began what has become a business and personal relationship that has spanned almost 30 years. Gary, a Mitchell, SD native, began his career as a staff accountant with Touche Ross in Minneapolis, and later joined the firm of Wohlenberg Gage & Co in 1971. As managing partner of the Mitchell office, Gary hired Bill Lurken in May, 1974, and Dave Olson in January, 1977, as staff accountants. Bill was a Minnesota native and graduate of Mankato State University. Dave was a native of Mobridge, SD and graduate of the University of South Dakota. When Dave joined the firm, there were six accountants, including Jerry Smith and Pat Carlon, both of whom later established independent practices in the Mitchell area.

At this time, all work was processed manually including preparation of tax returns and annual depreciation schedules. Financial statements were prepared on electric typewriters and most accountants worked with early vintage electric calculators. Digital calculators, fax machines, cell phones, email, text and tweets were yet to be experienced. Word processor technology survived for an even shorter time frame than that of the bag cell phones. WG & Co’s first electronically prepared tax returns were generated in 1980 and involved mailing a pro forma to the Sioux Falls office and them returning the printed copy. And with each of these new innovations, work quality and client time expectations began to accelerate.

Gary, Bill and Dave established their early business relationship on professionalism and mutual respect, and the principle of “quality services in a cost-effective manner”. Shortly after forming the partnership, ELO Prof LLC ventured into modern technology. Gary, Bill and Dave spent six months evaluating the “new computer age” before purchasing their first computer, a Radio Shack Tandy computer in 1982. Shortly thereafter, the three partners traveled to Minneapolis and spent two days looking at IBM and Compaq computers. A decision was ultimately made to purchase a 10MG (megabyte!!) Compaq computer with the assurance from the salesperson that this would be the last computer we would ever need to buy??

Recognizing the need for improved quality audit services, the firm was fortunate to recruit Jay Tolsma in 1986 as Audit Manager of the firm. Jay was a Stickney, SD native and graduate of Northwestern College, and was employed by the SD Department of Legislative Audit. Jay joined the partnership in 1994 and has been largely responsible for the successful growth of ELO Prof LLC’s attest service division.

Another major steps for the firm occurred in 1988 when ELO Prof LLC acquired Thomas Koehn’s accounting practice in Chamberlain. This was the first of several acquisitions for the firm over the next 5-7 years and has proven to be a professionally rewarding experience.

During the period 1988 through early 2000, the firm continued to grow in both the Mitchell, SD and Chamberlain, SD market areas. At a time when technology was increasing time and quality efficiencies, the firm grew from 10 to 15 staff members. New hires during this time included Pam Olinger and Lisa Brown in 1998. Jamie Eldeen joined the Chamberlain, SD office in 2001 and later relocated to the Mitchell, SD office.

During early 2002, ELO Prof LLC began to realize that its partners were not as young as they had once been and Dave and Jay began to discuss the future of ELO Prof LLC. After 18 months to two years of planning, they came to agree that they would work towards the long term objective of a “legacy firm”. Considerations included Gary and Bill’s retirement transition, new hire accountants and related training, and physical facilities.

This would be the firm’s first experience with “Succession Planning” and could well determine the future of ELO Prof LLC if the partners were unsuccessful in their business planning. After three years of consultation and negotiation, the partners adopted a plan to retire Bill Lurken’s equity interest in 2004. Bill and Linda continued to work with the firm as Associates through 2011. Subsequent to Bill’s retirement, Pam Olinger was admitted to the partnership in 2006 and has been involved in Gary’s succession plan in 2007, and the transition of Gary’s relationships through 2016.

The partner’s commitment to grow the firm included consideration of several strategic issues. Most important was the recruitment and retention of qualified staff members, and the necessary professional training. Beginning in 2005, ELO Prof LLC began hiring one to two individuals per year.

A second major consideration was the need for adequate office space as the existing building was no longer suitable for continued growth. After five years of planning, ELO Prof LLC constructed a new office building in 2007 which would serve as home to 12 team members. After 22 years in the community the firm built a new office in Chamberlain in 2010. Most recently, the firm constructed a seven office addition to its Mitchell, SD office in 2014.

Effective January 1, 2016, ELO Prof LLC completed the acquisition of the Huron CPA firm, Harrington & Associates.

Contact Us

Mitchell Office 605-996-7717

Sioux Falls Office 605-271-1302

Chamberlain Office 605-234-6055

Huron Office 605-352-8573

Miller Office 605-853-2130

Mitchell Office


Chamberlain Office


Huron Office


Sioux Falls Office


Miller Office