Mainline Protestant Population by State and County

Nelson County, North Dakota recorded the highest Mainline Protestant share of any US county in 2020, at 69.45 percent, according to the Association of Religion Data Archives. North Dakota also posted the highest state level share that year, at 21.01 percent. All ten of the highest ranking counties are in North Dakota, Minnesota, Iowa, or South Dakota.

Protestant Christianity in the United States splits into three main traditions tracked separately by researchers. Mainline Protestant congregations, rooted mostly in the United Methodist Church, the Evangelical Lutheran Church in America, and the Presbyterian Church (USA), are the oldest of the three, tracing back to the colonial churches many of the nation’s founders belonged to.

Key Takeaways

• Nelson County, North Dakota posted the highest Mainline Protestant share of any US county in 2020, at 69.45 percent.
• All ten of the highest counties are in North Dakota, Minnesota, Iowa, or South Dakota, with populations ranging from 1,798 in Steele County, North Dakota to 10,679 in Winnebago County, Iowa.
• North Dakota posted the highest state level Mainline Protestant share in 2020, at 21.01 percent, with South Dakota second at 17.94 percent.
• Utah recorded the lowest state share, at 0.50 percent.
• The United Methodist Church and the Evangelical Lutheran Church in America are the two largest Mainline Protestant bodies nationally.

What Makes a Protestant Denomination Mainline

Mainline Protestant denominations emphasize social and economic justice and a tolerance of varied individual beliefs. They tend toward broader theological interpretation than Evangelical Protestant denominations. One academic classification system ties the split directly to a five point scale of Biblical inerrancy, the literal authority of scripture, with Mainline denominations clustering at the low end and Evangelical denominations at the high end.

Examples include the Presbyterian Church (USA), the United Methodist Church, the Reformed Church in America, the Episcopal Church, the United Church of Christ, and the Evangelical Lutheran Church in America. Southern Baptist Convention congregations fall under Evangelical Protestant instead. Historically Black Protestant denominations, including the National Baptist Convention, are tracked as a third, separate tradition.

Nine of the ten highest counties for 2020 fall within roughly 300 miles of each other, spanning the eastern half of North Dakota into western Minnesota and northwest Iowa. That cluster traces back to Norwegian, Swedish, and German settlement patterns, which carried Lutheran and Reformed congregations into the region in the late 1800s.

Which US County Has the Most Mainline Protestants

Which US States Have the Most Mainline Protestants

North Dakota and South Dakota have led every state in Mainline Protestant share for every census since 1980, though the share itself has fallen by nearly half in both states over that stretch. Utah, Nevada, and California fall at the opposite end, all under 1.5 percent.

Here is a static map showing the Mainline Protestant population by U.S. state.

Utah’s low share reflects the same factor as its low Evangelical Protestant share, a Latter-day Saint majority that the census tracks as its own category, separate from all three Protestant traditions.