(written from a Production point of view)
First Street was a Detroit road mentioned on a medical file prepared for "Carpenter Street". While a number of different forms were seen on screen, none of them were readable or even especially recognizable, so it remains unclear if the road was featured in the episode.
The street was said to be located in the 40210 ZIP code area. (In the real world, the 40210 ZIP code area is located in Louisville, Kentucky). In 2004, two blood donors to the Porter Street blood bank lived on this street - Bill Smith (#1425) and Jef Duncan (#4570). (ENT: "Carpenter Street")