It is my understanding that: He flew a regular daily mail route from St. Louis to Springfield, to Peoria and on to Chicago, then back to St. Louis. The flashing light at the top of the Commerce Bank Building, called "Lindy's light" helped him navigate. Please correct me if I'm wrong or if you want to fill in more details.
@JnJ :
Yes, that is my understanding as well. Lindbergh continued as Robertson Aircraft Corp's chief pilot until February 1927 when he left for San Diego to oversee construction of his
Spirit of St. Louis. On February 20-21, 1928 the now celebrity pilot worked his old mail route in an awareness campaign for aviation.