Final answer:
The period that saw the rise of newspaper columnists was the 1920s and 1930s, thanks to the groundwork laid by muckrakers during the Progressive Era and the subsequent growth of the press.
Step-by-step explanation:
The rise of newspaper columnists can be most notably associated with the 1920s and 1930s, a period that witnessed the golden age of print journalism. The 1920s marked the era of the muckrakers, journalists focused on uncovering societal ills and corruption, stimulating public interest and leading to societal reforms during the Progressive Era. This period of investigative journalism paved the way for the newspaper columnist, who gained prominence and influence through their regular contributions to newspapers. By the 1930s, with the expansion of the press and its role in shaping public opinion through columns and editorials, newspaper columnists had firmly established their role in society.