Light twins have always had retractable landing gear and while some single engine aircraft did, many others did not. Beechcraft made them popular with its Bonanza series, brought to market just after WWII.
The Beechcraft Bonanza uses an electric retract system that must be maintained at regular intervals to avoid problems.
It is interesting to note that the pre-war single engine D-17 Staggerwing Beechcraft also had retractable landing gear along with its biplane configuration. The term, Staggerwing, refers to the position of the lower wing which is located ahead of that of the top wing. The reason being that most biplanes had their landing gear attached to the fuselage while the D-17 had the landing gear attached to the lower wing in order to position the main wheels in the correct relationship to the CG of the aircraft. When the Staggerwing was upgraded to retractable in the mid 1930s, the forward positioned lower wing made it very convenient to fold the wheel back into the wing. Grumman’s military fighter biplanes had to use a very complex and heavy retractable system so the wheels could be pulled up into the fuselage.
When designing light single-engine aircraft to include retractable landing gear, aircraft manufacturers were faced with several obstacles,
The Beech Sierra has trailing-arm main landing gear legs. This feature assures very smooth landings.