Ok, so Detroit has a lot of FIRSTS, dating way back to its colonial days. Let's try and round them up here! Be sure to provide a DATE and DESCRIPTION!
Below are some ones I thought of off-hand...
1701. First settlement established on the Lower Peninsula of Michigan.
1805-1847. First capitol of the Michigan Territory/State.
1866. First soda pop in America (Vernor's)
1879. First city in the U.S. to receive telephone numbers.
1909. First mile of paved concrete - Woodward between Six and Seven mile
1913. Henry Ford's Highland Park Plant is the first in the world to utilize the assembly line process.
1920 (?). First electronic traffic signal, Campus Martius.
1930. First international automobile tunnel in the world constructed between Windsor & Detroit.
1941. First urban depressed freeway - Davison Fwy - is constructed, spurring the development of no less than three more major interstates in the city.
Keep em coming! There are more!