Pike's Peak, apparently, is actually spelled Pikes Peak. No apostrophe. The US Board on Geographic Names abolished apostrophes in most place names all the way back in 1891. Nothing appears to have changed since then. Their Domestic Geographic Names: Principles, Policies, and Procedures (PDF) has this to say on the subject:
Apostrophes suggesting possession or association are not to be used within the body of a proper geographic name (Henrys Fork: not Henry's Fork). The word or words that form a geographic name change their connotative function and together become a single denotative unit. They change from words having specific dictionary meaning to fixed labels used to refer to geographic entities. The need to imply possession or association no longer exists. Thus, we write " Jamestown" instead of " James' town" or even "Richardsons Creek" instead of " Richard's son's creek." The whole name can be made possessive or associative with an apostrophe at the end as in " Rogers Point's rocky shore." Apostrophes may be used within the body of a geographic name to denote a missing letter ( Lake O' the Woods) or when they normally exist in a surname used as part of a geographic name (O'Malley Hollow).
And it's not just the United States. In Guidelines for the Consistent Use of Place Names (PDF), Australia also abolishes apostrophes, though for very different reasons:
In all cases of place names containing an element that has historically been written with a final - 's or -s', the apostrophe is to be deleted, e.g. Howes Valley, Rushcutters Bay, Ladys Pass. This is to facilitate the consistent matching and retrieval of placenames in database systems such as those used by the emergency services.
And here in the UK, the city of Birmingham recently abolished the use of the possessive apostrophe on road signs, much to the dismay of apostrophe protectors and militant grammarians.
The opponents of the apostrophe -- of which there are more than I ever imagined -- seem to be equally militant. In fact, they go so far as to demand that we kill the apostrophe. It's been suggested that killing off the apostrophe is the only possible cure for the greengrocers' apostrophe.
This is nothing new. George Bernard Shaw railed against apostrophes:
I have written aint, dont, havent, shant, shouldnt, and wont for twenty years with perfect impunity, using the apostrophe only when its omission would suggest another word: for example hell for he’ll. There is not the faintest reason for persisting in the ugly and silly trick of papering pages with these uncouth bacilli.
I do love George Bernard Shaw -- even more so when he's ranting -- but I'm not entirely convinced. I'm decidedly not a militant grammarian, but I don't think English would look like English without the apostrophe. Maybe I'm just old school.
The apostrophe can be confusing. Until the apostrophe is killed off by the haters, the Plain English Campaign has a helpful guide (PDF). Alternatively, you could just follow William Safire's sage advice:
Reserve the apostrophe for it's proper use and omit it when its not needed.
Update: In the interests of presenting both sides of the arguement, I felt obliged to mention The Apostrophe Protection Society. I hasten to point out that I in no way endorse the web design or indeed the HTML of their website.
Update 2: Michael Quinion has written an excellent essay on the possessive apostrophe, which is where I discovered Australia's Guidelines for the Consistent Use of Place Names (PDF). *[HTML]: Hypertext Markup Language *[UK]: United Kingdom