It seems Spikes Peak was a later addition to Wonderland, and may have replaced Creepy Crawly Forest: Chris Floyd, a content designer who left in late 2007, remembered Creepy Crawly Forest being part of Wonderland, but hadn't heard of Spikes Peak and thought it must have came after his time working on the game. Concept art of Brick Mesa also shows the Creepy Crawly Forest ruined castle wall where the border with Spikes Peak is on later Wonderland maps. Additionally, the few object definitions that exist for Creepy Crawly Forest have internal IDs in the 1770s and from 1915 to 1920, while the Yeti object definition for Spikes Peak is much later, at 3204.
Spikes Peak may have been named after Pikes Peak, a mountain in Colorado close to the NetDevil studio.
A map of Wonderland showing the location of Spikes Peak
Concept art by Dave Kang
Concept art of the crashed Mars Mission ship between YouReeka and Spikes Peak, by Jerry Meyer