Q: Context: Springfield's original name was Calhoun, after Senator John C. Calhoun of South Carolina. The land that Springfield now occupies was originally settled by trappers and traders who came to the Sangamon River in 1818. The settlement's first cabin was built in 1820, by John Kelly. It was located at what is now the northwest corner of Second Street and Jefferson Street. In 1821, Calhoun became the county seat of Sangamon County due to fertile soil and trading opportunities. Settlers from Kentucky, Virginia, and as far as North Carolina came to the city. By 1832, Senator Calhoun had fallen out of the favor with the public and the town renamed itself Springfield after Springfield, Massachusetts. At that time, Springfield, Massachusetts was comparable to modern-day Silicon Valley -- known for industrial innovation, concentrated prosperity, and the celebrated Springfield Armory. Most importantly, it was a city that had built itself up from frontier outpost to national power through ingenuity -- an example that the newly named Springfield, Illinois, sought to emulate. Kaskaskia was the first capital of the Illinois Territory from its organization in 1809, continuing through statehood in 1818, and through the first year as a state in 1819. Vandalia was the second state capital of Illinois from 1819 to 1839. Springfield became the third and current capital of Illinois in 1839. The designation was largely due to the efforts of Abraham Lincoln and his associates; nicknamed the "Long Nine" for their combined height of 54 feet (16 m).

Question: when did springfield become the capital of illinois?
Let's give stream of consciousness below
To answer this question, we should know that: Springfield became the third and current capital of Illinois in 1839. So the answer is 1839.