Lemont's first settlers arrived in 1833. The town, then called Athens, began its development along the site of the Illinois & Michigan Canal that flows through the town. The canal, begun in 1836 and completed in 1848, linked the Illinois River and Lake Michigan to make a direct waterway to the Mississippi River. Almost all the early town pioneers came to work on the canal, either as contract holders or laborers. The contractors were mostly from New England or the Ohio border towns. The unskilled laborers were the newly immigrated Irish, German, Scandinavians, along with French and English Canadians who came looking for a new life, fleeing poverty and political persecution. By 1848, Lemont's population reached 3,000 people.

While digging the canal, an exceptionally fine grade of dolomite limestone was discovered near the surface. This discovery led to the development of the stone quarries. During the period from about 1850 to 1900 this stone, known as Joliet-Lemont limestone and locally as Athens Marble, became one of the chief building materials used in many landmark buildings both locally and in the surrounding area. The Chicago Water Tower, the gate to the Stockyards, Holy Name Cathedral, part of the Auditorium Building in Chicago, Old Main at Northwestern University and part of the Capitol building at Springfield are some of the structures constructed of Lemont stone.

The quarry industry, like the canal before, attracted more immigrant groups, mainly from southern and south central Europe: Poland, Bohemia, Czechoslovakia, Austria and Italy. Work was hard and the pay low. Lemont made pages of labor history with the struggles between the quarry workers and the owners. In 1885, the Illinois Militia was ordered to Lemont to break a strike. Three people were killed and scores injured. In 1893, Governor Altgeld came to Lemont personally to mediate a strike after a fight between Sanitary Ship Canal contractors and quarry workers led to three more deaths.

The natural terrain of the DesPlaines Valley was ideal for constructing the I & M Canal and also for the construction of railroads. Two rail lines have been a big part of the town's history: the Chicago & Alton built in the 1850s and the Santa Fe in the 1890s. The construction of these railroads brought workers to the area as it became an important cattle, grain and dairy shipping point.

In the 1890s, construction began on the Sanitary & Ship Canal. Lemont became a "wide open" town in those years to accommodate a population of 10,000 people. The downtown area known as "Smokey Row" with its bars and brothels gained notoriety as the wildest, most sinful street in the country. After the canal was completed, some of the workers remained to settle in Lemont.

The 20th century brought industrialization with growth of steel, chemical and oil companies, and newer high tech complexes including Argonne National Laboratory.

Two volumes are available with a more detailed history of Lemont. The "Lemont History Book" (Buschman) and "Lemont and Its People" (Kallick).