Merger talks have come to a halt in a deal that would have created a large network of hospitals and clinics spanning six states, including western Minnesota, according to officials with South Dakota-based Sanford Health.

Sanford Health unveiled plans over the summer to merge with Iowa-based UnityPoint Health, which would have resulted in an operation with $11 billion in annual revenue, but Sanford Health’s chief executive said the parties couldn’t reach a final agreement.

“Our conversations regarding a potential merger with UnityPoint Health have ended,” said Kelby Krabbenhoft, president and CEO at Sanford Health, in a statement. “The executive management teams and physicians worked diligently for 18 months to provide a merger recommendation to the boards. We are disappointed that the UnityPoint Health board failed to embrace the vision.”

Backed by philanthropist Denny Sanford, Sioux Falls-based Sanford Health runs a large network of hospitals, clinics and nursing homes, including operations in South Dakota, North Dakota and western Minnesota. As of July, the Minnesota operations included 18 hospitals and 171 clinics.

UnityPoint Health runs hospitals and clinics in Iowa, Illinois and Wisconsin. The Des Moines-based health system also jointly owns a health insurance company with Bloomington-based HealthPartners.