It should be hyphenated when it's being used as an adjective. For example: nineteenth-century writers.
The nineteenth century was from 1800 - 1899.
The hyphen would be located between the mid and the century.'Mid-century'.
Nineteenth-Century Literature was created in 1945.
The Foundations of the Nineteenth Century was created in 1899.
The Nineteenth Century - periodical - was created in 1877.
The Nineteenth Century - periodical - ended in 1972.
Woman in the Nineteenth Century was created in 1843.
The Italian word for the nineteenth century is "diciannovesimo secolo."
Where were most of Europe's colonies by the end of the nineteenth century?
No, "mid-nineteenth century" is not capitalized unless it is at the beginning of a sentence.
Birmingham Journal - nineteenth century - was created in 1825.
Birmingham Journal - nineteenth century - ended in 1869.