Wigs have been worn since well before Christ was born.
Most notoriously by the Egyptians (men & women) who shaved off their hair because of the heat and then wore wigs for formal occasions.
They exposed their hairlines, as have wearers right up to the present day.
The only thing that has changed is the success at creating a more natural appearing hairline.
More recently, actors on stage & screen have driven the development of hairpieces.
Since film & TV became popular, actors have worn pieces with exposed hairlines.
Wig making has had to keep up with the increasing clarity & definition of filming, until we have the products we know of today.
High Definition will push that even further.
I think you'd have to be more specific in your question to get a more specific answer.
I read somewhere that in the early part of the 20th century they made men's toupees with bases of hair lace - a netting actually made with human hair. They were supposedly excellent, but too expensive to be viable for most people. John D Rockefeller wore one.
The big breakthrough came when Max Factor developed the lace toupee for Hollywood actors in the 1950s. I guess his lace was pretty similar to what you can get nowadays from a company like Toplace - some sort of manmade fiber.
well my first hairpiece was monofilament, which is said to be yesteryears technology, adn I just wanted to know when, in general, they started to make lace for the general public, so when teh public were able to get their hands on a lace system and start to get hairlines.
I assume before than people just brushed the hair forward and never exposed their hairlines.
Back in the early-mid 90s I was buying hair systems by Rene Duval that used a product they called 'Hollywood Lace' That was much finer than monofilament and allowed you to expose the hairline.
I was buying the at wholesale prices for about as much as I would now pay for an average priced piece sold at retail.
The same company is still selling the same product today, though they've changed the name to Celebrity Lace, presumably to avoid confusion with the retailer called 'Hollywood Lace'.