Like Sprint and AT&T, MCI originally completed and routed long distance calls via a simple network of microwave towers. As such MCI was once known as Microwave Communications, Inc. denoting the use of this network of microwave towers as the backbone of the companies operations. However, this changed in the early 80s when Sprint replaced their network of microwave towers with an all fiber optic backbone. MCI followed suit even using the demolishion of decommissioned towers in a TV commercial trumpeting "service improvements". Despite the emergence of fiber optics as the perfered transmission medium, MCI and AT&T continue to use many of their microwave sites as backups or backhaul for remote areas. Many MCI switches are located at microwave junctions.
Unlike the inverted Y used by Sprint or the plain spaghetti mess employed by AT&T in the Mid-Atlantic area, MCI's backbone is deployed much like a sloppy cross. N/S routes are used to interconnect switch sites and are of original MCI construction. E/W routes are used to link POPs back to the switch (in Virginia anyway) and appear to date back to the SouthernNET (Telecom*USA) days.
| Route | Segment | Map | Comment(s) |
|---|---|---|---|
| Washington, D.C. - Perryman, MD | N | Switch (MCIMetro ATS) to switch | |
| Baltimore, MD - Perryman, MD | N | POP to switch | |
| Washington, D.C. - Baltimore, MD | N | Switch (MCIMetro ATS) to POP | |
| Washington, D.C. - Richmond | N | Switch (MCIMetro ATS) to switch | |
| Washington, D.C. - Fredericksburg | N | Switch (MCIMetro ATS) to POP | |
| Fredericksburg - Richmond | N | POP to switch | |
| Richmond - Charlottesville | Richmond - Charlottesville | N | Switch to POP, ex SouthernNET |
| Richmond - Lightfoot (James City Co.) | Richmond - James City Co. | N | Switch to POP, ex SouthernNET |
| Richmond - Cary, NC | Richmond - Emporia | N | Switch to switch |
| Charlottesville - Lynchburg | Charlottesville - Lynchburg | N | POP to POP |