Soon, Kennicott was providing specimens for the Smithsonian Institution via assistant secretary Spencer Fullerton Baird.

Kennicott advocated for the study and protection of native prairie animals in an era when farmers sought to eradicate them.

His father, John Albert, was interested in botany and maintained a large land holding in Northfield Township, Cook County, Illinois, which came to be known as "The Grove".

[1] Jared Potter Kirtland, a friend of Kennicott's father and one of the leading naturalists in the west, agreed to take Robert as an understudy in late 1852.

The Board of Trustees of Northwestern University approached Kennicott in early 1857, asking him to help them create a natural history museum.

For the next two winters, Kennicott worked at the Smithsonian in Washington, D.C., helping Baird organize its amphibian and reptile collections.

[1] In April 1859 he set off on an expedition to collect natural history specimens in the subarctic boreal forests of northwestern Canada in what is now the Mackenzie and Yukon river valleys and in the Arctic tundra beyond.

Kennicott became popular with Hudson's Bay Company fur traders in the area and encouraged them to collect and send natural history specimens and First Nations artifacts to the Smithsonian.

[1] Robert and his younger brother lived in the Smithsonian Castle during the war along with Edward Drinker Cope and other noted naturalists.

[1] While working at the Smithsonian Institution under Assistant Secretary Spencer F. Baird, Robert Kennicott wrote the original descriptions of many new snake taxa brought back by expeditions to the American West.

His body was returned to his family's home in Illinois, enclosed in a metal canister and shipped via Russia and Japan rather than sent back on undeveloped trails through Canada.

An investigation in 2001–2016 into the cause of his death suggested that Kennicott may have suffered from long QT syndrome, a congenital cardiac condition that can cause an irregular heartbeat, weakness, and fainting spells.

According to a summary of the research in the Washington Post, "the combination of stress, physical exhaustion and toxic 'medicine' was too much for the young scientist's weak heart," and led to his death by cardiac arrest.