For much of American history, large religious gatherings happened in fields and groves rather than buildings. The outdoor setting was a practical necessity first, and it went on to shape the events themselves.
No building on the frontier could hold the crowd
Settlements were small and scattered, and their meeting houses seated a few dozen people. A gathering drawing families from across a county had nowhere indoors to go.
A grove with shade and water could hold whatever number arrived. Capacity was set by the ground rather than by walls.
Building anything permanent would also have been wasted. Gatherings happened once or twice a year, leaving a large structure empty for the remaining months.
Distance made a multi-day format necessary
Families traveling a day or more by wagon could not attend a single service and return home. Once the journey was made, staying several days was the only sensible arrangement.
That produced the camp itself, with tents, cooking arrangements and stock to be watered and fed. Attendance meant relocating a household temporarily.
Timing followed agriculture, falling after planting or after harvest when labor could be spared. The religious calendar bent to the farming one.
The setting changed how preaching worked
Speaking outdoors without amplification to a large, mobile crowd requires volume, repetition and strong physical delivery. A quiet expository style would simply not carry.
Preachers spoke from raised stands so they could be seen as well as heard. Several might preach in sequence or simultaneously in different parts of the ground.
Singing did organizing work that a building's structure normally provides. A crowd that could sing together from memory could be gathered, moved and held.
The ground developed its own architecture
Regularly used sites acquired permanent features over time, including a covered stand, benches arranged in an arc and marked lots for family tents. Layout followed use.
Many sites eventually built open-sided tabernacles, roofed against sun and rain but still without walls. The form kept the openness while adding shelter.
Some grounds became small seasonal settlements with cottages replacing tents. A number of American communities began in exactly this way.
The form persists in modified shapes
Summer camps, outdoor revivals, denominational conference grounds and religious retreat centers all descend from this pattern. The seasonal gathering away from home remains recognizable.
Air conditioning and highways removed the original constraints. Large indoor venues can now host what once required a field.
Where outdoor gatherings continue, the reasoning has inverted. The open air is now chosen for what it does to a gathering rather than accepted for lack of a building.