Hudson River Brick and North Carolina Brick

The penetration of Southern bricks into New York was the last big event which directly brought down the remains of the Hudson River Brick industry after 1960s

Comparing with Hudson River Brick, there are some big advantages for North Carolina brick:

Northeastern clay is homogeneous and in North Carolina, the clay bed vary from 80 to 140 ft in depth. no other glacial deposits. Calcium score: NC (average) 0.6, HR4.9-8.

NC clay has a larger particle size which is good at efficiencies of extrusion.

NC clay does not have high silica content, which resulted in a reduction of firing time.

NC clay provide little resistance in the extrusion machinery.

Reference: "The Great Hudson River Brick Industry", George V. Hutton