The vast majority of presidents in the United States have been clean-shaven. Even though it is entirely possible that some of the earlier presidents had facial hair from time to time, in their official portraits, they usually do not have any facial hair at all. It is unclear exactly why so many presidents decided not to have facial hair, and some of them may have decided to remain clean-shaven purely because the people who came before them were also clean-shaven. Of note, facial hair became much more popular during the 19th century, which is why a lot of presidential portraits during this time had facial hair in them.
The very first president to have any notable facial hair was John Quincy Adams. He served as president from 1825 to 1829. He had long sideburns on the side of his face, but he did not have a mustache or a beard. The first true departure from the look of the clean-shaven president was Abraham Lincoln. He was elected twice, but he was assassinated shortly after the end of the Civil War. Supposedly, he was told to grow a beard like a child. She believed that if he had a beard, he would have a greater shot of being elected president. He started a trend, where the vast majority of presidents for the next 50 years would have facial hair.
After Abraham Lincoln, just about every president for the next 50 years would have facial hair. For example, Ulysses S Grant came after Abraham Lincoln, and he had facial hair. The only presidents during the next 48 years who did not have facial hair were Andrew Johnson, who served as vice president to Abraham Lincoln before becoming president himself, and William McKinley, who was assassinated in 1901. Rutherford B Hayes, James Garfield, and Theodore Roosevelt all had some form of facial hair. William Howard Taft had facial hair as well. He served from 1909 to 1913, and he is the very last president to have had facial hair.
At the beginning of the 20th century, facial hair would quickly fall out of favor in the White House. There is some speculation that facial hair became less popular because of a PBS report that was published around the same time. There was some concern that people who had facial hair would have a greater chance of contracting tuberculosis. This is a chronic infection that impacts the respiratory system, and it is possible that prominent leaders in the United States were encouraged to stay away from facial hair to avoid contracting the illness. Very briefly, Harry Truman had a goatee; however, it is very difficult to find a picture of him with any form of facial hair. It remains to be seen if facial hair will make a return to the White House in the future.