Possible Clues:

• It's bigger than family
• A number of families from America turned back at frontier
• Taxonomic category
• Small group of families upset American immigration point?
• Thing taken at a deli?
• Taxonomic category above family
• Botanical group? Our type will shoot up on strip in garden
• Group of animals American brought over frontier
• Group of creatures backing America to the limit
• Taxonomic group originally unknown in southern confines