The hight of wig wearing was certainly the 18th century. But wigs and hair pieces have been worn by men and women in various places for even longer than that. There was also of course a good deal of going in and out of style. For men I would say the first decades of the 19th century were when wigs went out of style. For women they went ‘out’ around the same time, but hair pieces, though not full wigs, remained fairly common for women. Hair pieces made a big resurgence from the late 19th to early 20th centuries when hair styles for wealthy women usually required a good deal of padding out. They were even sold by mail (as were wigs) in the Sears and Montgomery Ward catalogues which marketed to the middle classes. Orthodox Jewish married women still often wear wigs (usually referred to by their Yiddish name ‘shaitels’)and have done since at least the early 19th century, and many African American women throughout the twentieth century wore hair in various ways. The the modern trend of hair extensions is quite similar to the late Victorian trend of padding out the hair with locks, hair rats, or curls. As to why wigs got a bit of a bad connotation, it’s complex. One Lilly reason is that throughout the 19th century they became less associated with aristocracy and more associated with the loss of hair due to age or illness. The many illnesses of the 19th century were often accompanied by hair loss due to extreme stress on the body, high fever, or rapid weight loss. Women’s long hair was sometime cut close to the head during an illness to keep her cool in hopes to lower a fever. Wearing hair became seen as something done out of necessity rather than opulence and it continues in some circles to hold that connotation.