How long have they been making felt baseball pennants?
The first known pennants appeared at ballparks at the turn of
the century, and from 1905-1910 the first pennants bearing team or
city names were produced. The first World Series pennant for the
Boston Braves appeared in 1914. In the 1970's the traditional felt
pennants were replaced by Synthetics which were added to the
fabric, making a stronger, thinner, and less expensive pennant.
For more information on vintage baseball pennants visit the link
I left below.