When I hear the word ATV, short for all terrain vehicle, I automatically think four wheeler because those are the ATVs I grew up with and are the most common incarnation of the ATV. However, ATVs were originally invented as three wheelers, with the first ATV from a major manufacturer, Honda, shown below.
This is the ATC90 (All terrain cylinder 90), released originally by Honda in 1970. It was designed with large soft tires to make up for its lack of suspension. The ATV was made popular by its appearances in various movies and TV shows.
Slowly over the years the aesthetics of the ATV evolved, becoming marginally sleeker with knobbier tires and lights. Show below is a 1977 ATC90 model by Honda. It still had no suspension.
Eventually people began to realize that the ATVs could be used for more than just getting around and having fun; they could be used for work. At this point the racks that are now a mainstay on ATVs were born, seen below in this 1982 Honda ATC200 Big Red. By this point in their development the old ball like tires had been left behind and suspension was introduced for the first time.
It was around this time that the first four wheel ATV was produced. It was produced by Suzuki and was reminiscent of the first four wheeler in its simple design. The model was called the 1982 QuadRunner LT125 and can be seen below. It included modern innovations such as suspension but no racks
By 1987 the four wheeler industry had caught up with the three wheelers in being used for work, with racks being added and looks refined. This was seen for the first time in 1987 with the Honda foreman 4×4, seen below.
From this point on the evolution of the aesthetics of the ATV was defined by it becoming more powerful, more capable, and sleeker every year leading to the current incarnation. Shown below is a 2016 Suzuki KingQuad 4×4.