Here I have attempted to make a complete list of Non-Crane Gruiformes present in American and Canadian collections. Cranes are already covered in a different thread by @Great Argus. Only information 2017 or newer was used. Information on missing holders or species, as well as information on subspecies or populations is welcomed.
I suspect the reason this list appears so small isn't the lack of these species in captivity, but rather the lack of publicity about these species. Zoos don't really advertise these species (with a certain exception from Guam), and they really don't seem that popular of animals to photograph on ZooChat, either. We shall see if my hypothesis is correct.
Gray-Winged Trumpeter (6 holders)
Bronx Zoo
Caldwell Zoo
Dallas World Aquarium
Minnesota Zoo
National Aviary
Sylvan Heights Bird Park
Guam Rail (9 holders)
Cincinnati Zoo and Botanical Garden
Guam Zoo
Lincoln Park Zoo
National Aviary
Philadelphia Zoo
Racine Zoo
San Antonio Zoo
Sedgwick County Zoo
Smithsonian Conservation Biology Institute
Buff-Banded Rail (1 holder)
Central Park Zoo
Ridgeway's Rail (1 holder)
Living Coast Discovery Center (levipes)
Gray-Necked Wood Rail (4 holders)
Bronx Zoo
Henry Vilas Zoo
Omaha's Henry Doorly Zoo
Toronto Zoo
Giant Wood Rail (3 holders)
Assiniboine Park Zoo
Dallas World Aquarium
Special Memories Zoo
Sora (2 holders)
Buttonwood Park Zoo
Columbus Zoo & Aquarium
Gray-Headed Swamphen (2 holders)
Los Angeles Zoo & Botanical Gardens
Wildlife World Zoo & Aquarium
Allen's Gallinule (2 holders)
Oregon Zoo
Philadelphia Zoo
Purple Gallinule (2 holders)
Audubon Zoo
Toronto Zoo
Common Gallinule (4 holders)
Gladys Porter Zoo
Milwaukee County Zoo
Patricia and Phillip Frost Museum of Science
Saint Louis Zoo
American Coot (1 holder)
Bay Beach Wildlife Sanctuary
I suspect the reason this list appears so small isn't the lack of these species in captivity, but rather the lack of publicity about these species. Zoos don't really advertise these species (with a certain exception from Guam), and they really don't seem that popular of animals to photograph on ZooChat, either. We shall see if my hypothesis is correct.
Gray-Winged Trumpeter (6 holders)
Bronx Zoo
Caldwell Zoo
Dallas World Aquarium
Minnesota Zoo
National Aviary
Sylvan Heights Bird Park
Guam Rail (9 holders)
Cincinnati Zoo and Botanical Garden
Guam Zoo
Lincoln Park Zoo
National Aviary
Philadelphia Zoo
Racine Zoo
San Antonio Zoo
Sedgwick County Zoo
Smithsonian Conservation Biology Institute
Buff-Banded Rail (1 holder)
Central Park Zoo
Ridgeway's Rail (1 holder)
Living Coast Discovery Center (levipes)
Gray-Necked Wood Rail (4 holders)
Bronx Zoo
Henry Vilas Zoo
Omaha's Henry Doorly Zoo
Toronto Zoo
Giant Wood Rail (3 holders)
Assiniboine Park Zoo
Dallas World Aquarium
Special Memories Zoo
Sora (2 holders)
Buttonwood Park Zoo
Columbus Zoo & Aquarium
Gray-Headed Swamphen (2 holders)
Los Angeles Zoo & Botanical Gardens
Wildlife World Zoo & Aquarium
Allen's Gallinule (2 holders)
Oregon Zoo
Philadelphia Zoo
Purple Gallinule (2 holders)
Audubon Zoo
Toronto Zoo
Common Gallinule (4 holders)
Gladys Porter Zoo
Milwaukee County Zoo
Patricia and Phillip Frost Museum of Science
Saint Louis Zoo
American Coot (1 holder)
Bay Beach Wildlife Sanctuary