The rover's wheels and suspension use a "rocker-bogie system", which is quite unique since it does not use any springs. Instead, its joints rotate and conform to the contour of the ground, providing the greatest degree of stability for traversing rocky. A four-wheel body was turned down since a six-wheel design would provide greater stability and obstacle-crossing capability. Most six-wheeled vehicles can overcome obstacles that are three times larger than those crossable by four-wheeled vehicles (on Earth anyways). For example, one side of Sojourner could tip as much as 45 degrees as it climbed over a rock without tipping over. The wheels are 13 centimeters (5 inches) in diameter and made of aluminum. Stainless steel treads and cleats on the wheels to provide traction and each wheel can move up and down independently of all the others. Three motion sensors along Sojourner's frame can detect excessive tilt and stop the rover before it gets dangerously close to tipping over. Amazingly, Sojourner is capable of scaling a boulder on Mars that is more than 20 centimeters (8 inches) high and keep on going.

The Pathfinder project was one of the first of NASA's Discover Program Missions. These mission are defined as low cost (anything less than $150 million US) and have a short three year or less development time. Both of which Sojourner met fully since the Mars Pathfinder lander was built at a cost of $171 million, however, this also includes the $25 million to built the microrover. Pathfinder landed a single vehicle, which was called the Lander, on the surface of Mars on July 4th, 1997. Some of the mission parameters for Sojourner were to carry out a number of engineering, technology and science experiments. One of the "Primary technology objectives" for Pathfinder was to demonstrate a "low cost cruise stage and the Entry, Descent and Landing (EDL) systems required for putting a payload safely on the Martian surface."