Some of the greatest imports to Plymouth from the Americas and Europe during the latter half of the 19th century included maize, wheat, barley, sugar cane, <answer>guano</answer>, sodium nitrate and phosphate Aside from the dockyard in the town of Devonport, industries in Plymouth such as the gasworks, the railways and tramways and a number of small chemical works had begun to develop in the 19th century, continuing into the 20th century.
What animal byproduct was imported to Plymouth in the 19th century?
guano