The data from Gallup tracked church membership across the past 80 years, starting with 73% in 1937 and peaking just after World War II with 76% membership.
The past 20 years have seen a sharp dropoff, falling from 70% to 47% in that time.
The survey asked "Do you happen to be a member of a church, synagogue or mosque?"
Other questions covered the factors or reasons around religious attitudes and practices, with most respondents pointing to a lack of affiliation as the prime factor in their response.
Another major distinction arose between age groups: Church membership was strongest among those born before 1946, with 66% claiming membership, compared to 58% of baby boomers, 50% of Gen X and 36% of millennials.
However, the age difference still contains a decline in each age group: membership in the traditionalists (born before 1946) dropped from 77% in 2000 to that 66% figure today.
Baby boomers showed the smallest dropoff, trending down from 67% to 58% over the past two decades.
That trend is prevalent among all subgroups, as well, no matter gender, political affiliation or location.
The poll suggested that major factors in helping spiritual leaders regain some of that lost membership included "spiritual programs geared toward children and teenagers, community outreach and volunteer opportunities, and dynamic leaders were also factors in their attendance."
"A focus on some of these factors may also help local church leaders encourage people who share their faith to join their church."