Silver Ridge

While the humans may have abandoned the mining town of Silver Ridge long ago, the Decepticons think it's a great location for a base.

Silver Ridge is either located in Nebraska or North Dakota, depending on who you ask.

Dreamwave Armada comic
Shortly after arriving on Earth in search of Mini-Cons, the Decepticons set up a base in Silver Ridge, Nebraska. Sparkplug, Longarm, and Jolt infiltrated it in an attempt to rescue the Air Defense Mini-Con Team. Later, after most of the Decepticons left their base to go to the Moon, the Autobots attacked it so they could make use of its space bridge.

The Silver Ridge base was infiltrated again after the Decepticons found Over-Run's null-reality pods and took them back to base. In addition, three Heralds of Unicron made it into the base by taking the space bridge from Cybertron. Over-Run then used the null-reality pods to locate Optimus Prime, who was lost in another dimension, and brought him back to their dimension's Silver Ridge.

Panini Armada comic
The Decepticon base was hidden underneath the ghost town of Silver Ridge, North Dakota. Sparkplug, Longarm, and Jolt infiltrated it in an attempt to rescue Leader-1 and the other Mini-Cons enslaved by the Decepticons. Some time later, the Decepticons had relocated to a new base on the Moon.