Road Machinery & Supplies Co. was founded in Duluth, MN in 1926 by Michael M.Sill, a former salesman for Minneapolis Steel and Machinery Company.

RMS weathered the Great Depression of the 1930's and the shortages resulting from WWII, selling a variety of products and supplies such as motor graders, culverts and snow fencing.

Twin sons, Michael R. Sill and Mitchell J. Sill, entered the business in 1955 and the company expanded dramatically. While Mitchell managed Northern Minnesota, Mike opened up a Twin Cities store and managed Southern Minnesota.

RMS courted heavy equipment suppliers and by 1960 took on statewide representation of Clark (wheel loaders), Blaw Knox (asphalt pavers), and Link Belt (cranes and excavators).

RMS entered the truck equipment business in 1972 and expanded that operation in 1979 when they became the Midwest distributor for Telelect Products and other lines of truck mounted equipment in the Dakotas, Minnesota and Iowa.

In 1980, Road Machinery took on representation of Komatsu dozers, loaders and hydraulic excavators. Komatsu is the second largest manufacturer of construction equipment in the world.

In 1986, RMS started Aspen Equipment Co., following its acquisition of Airpower Equipment Corp. Aspen's focus was on general equipment such as air compressors, light towers, chippers, and truck cranes.

Road Machinery & Supplies Co. was separated in 1994, largely for estate planning purposes. Mitchell Sill and his family took ownership of Aspen Equipment and the former Truck Equipment Division (renamed Reach Equipment), and Mike Sill and his family retained RMS and its heavy construction, forestry, and mining products. Following the company separation, third generation President, Michael M. Sill II, was promoted to lead RMS.

The company entered the crushing and screening products and extendable boom forklift markets through the acquisition of Lambert Machinery in 1995. The following year, RMS acquired the Bucyrus International and Demag accounts from Dom Ex, Inc. In 1997, RMS acquired Herman M. Brown Company, one of Iowa's oldest and largest construction equipment distributor.

RMS serves the used parts needs of its customers through its Polar Parts division (1996) and the light and general equipment segment through its RMS Rentals subsidiary (1998).

In 2003, RMS purchased a national trench shield marketing company called Atlanta Equipment. RMS also started a company focused in Florida called US Shoring.

RMS today has grown to become one of the largest Komatsu dealers in the U.S., with nine offices, in MN (4), IA (3), MI (1) and IL (1). Through the dedication of its 205 employees and the commitment to represent the highest quality products in the industry, RMS has remained a preferred equipment supplier for over 78 years.