[2] The county was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada.

The county has evidence of human habitation from 10,000 years ago, the Archaic period of indigenous Americans.

In the early 19th century, European settlement started at a greater pace, after exploration during previous decades by French trappers and British and American fur traders.

Although the Loutre Island area is commonly associated with the German-founded towns of Rhineland and Starkenburg, established by immigrants of the mid-19th century and later, it was originally settled by Missouri's Anglo-southern settlers from places such as Kentucky or Virginia.

St. Martin's Church is also located in Starkenburg, built in 1873 and listed on the National Register of Historic Places.

Starkenburg is also the site of the Shrine of Our Lady of Sorrows Catholic Church, built in the early 20th century and listed on the NRHP.

For further devotions and pilgrimage, the community created an outdoor area for representations of the Stations of the Cross, Mount Calvary and Holy Sepulchre.

After the destructive Great Flood of 1993, Rhineland citizens used federal funds to relocate their houses 1.5 miles (2.4 km) inland away from the river.