I think they were Diane von Furstenburg dresses.
Other 70's designers (started getting famous in the 70's):
Halston
Emanuel Ungaro
Geoffrey Beene
Bill Blass
Ralph Lauren
Oscar de la Renta
Valentino
Pauline Trigere
Maud Frizon (shoes)
Mary McFadden
Yves St. Laurent
Vogue magazine was great in the 1970's. Beautiful models and clothes, unlike now.
Speaking of 70's clothes, how could we forget those polyester pantsuits for women? Yuck.
I'll have to take your word for it.
But whoever invented the pleated miniskirt though deserves a prize!