Tuesday was a gorgeous day for a landslide conference, and so a gaggle of media gathered round a bouquet of microphones standing on Route 65 as a state and county honcho gave the lowdown on the big pile of dirt behind them.

A more fitting metaphor for the fragmentation of Pennsylvania government would be hard to find. There are 2,566 municipalities in the state, maybe one for every ton of hillside that slid across the highway, though I haven't bothered to check the tonnage. (That kind of casual calculation is in keeping with what got us our landslide in the first place.)

If you want to know why this happened, you can't stop with geology. You have to move on to political science, to the bedrock of Pennsylvania statecraft, which is, of course, every municipality for itself.

Kilbuck is a community of roughly 700 souls with a desperate need to expand its tax base and give its homeowners some relief, so it had the bright idea of building a shopping center where a mental institution used to be.

Enter Wal-Mart. The situation was perfect. It could set up shop in a place that would attract and affect the traffic of tens of thousands, as well as the livelihoods of some unknown number of merchants up and down Ohio River Boulevard. Yet it wouldn't have to answer to anyone who didn't live in Kilbuck, which blocked the opposition pretty nicely.

That's Pennsylvania. Four out of five municipalities have fewer than 5,000 residents. Nine of ten have fewer than 10,000.

None of the 11 communities along the highway corridor north of Kilbuck can scrape together more than 3,900 people. Five have fewer than 1,000. Taken together, the entire Quaker Valley School District claims only 13,225. Heading south from Kilbuck toward the city, the biggest town is Bellevue, which claimed 8,770 in the last U.S. Census.

Getting none of the tax revenue but enduring all the bottlenecks didn't seem like a good idea to a lot of these people, even before the hillside fell down and went boom. (Or, according to another theory, went boom then fell down.) A group banded together more than four years ago as "Communities First!," and said Kilbuck was no place for a shopping center. But moving mountains is easier than nudging a system stacked against you.

"We citizens have no authority to challenge a developer's proposals unless we live practically on top of the site in question,'' wrote Molly Lundquist of Sewickley, a member of Communties First! "This holds true even when we can prove relative proximity and demonstrate that we might suffer significant safety, environmental and economic effects."

Allegheny County has invested $3 million in a comprehensive plan that, once complete, the state will be required to consider before it issues permits for development, county Chief Executive Dan Onorato said. But that guidepost for transportation and retail will arrive too late for this landslide.

It may also be too little, says Sean McLinden, a resident of Glenfield (population 236) and a member of Communities First! The county needs authority to establish and enforce countywide zoning. Communities shouldn't be able to relax construction requirements, as was done in Kilbuck, without a formal appeal process. Any county resident should have standing to appeal.

I won't slam the residents of Kilbuck for this mess. The community is doing pretty much what the state's Darwinian set-up encourages. Only here it's not survival of the fittest, but survival of the newest.

Kilbuck's northern neighbor, Ohio Township, just followed a residential building boom with a county-subsidized shopping center on a hill overlooking Interstate 279. Coincidentally, the landslide detour takes you right past it. If you look up, you can see a Target superstore atop the terraced hillside.

Earth-movers are now terracing the Kilbuck hillside, too, albeit a tad late.

Russ Hardiman, a Kilbuck supervisor who took office in 2004, ran on the single-issue platform of dissolving Kilbuck and having it become part of Ohio Township. He never got a second supervisor's vote, and the larger, more prosperous township had little incentive to merge anyway. It has less now.

"We're a disaster away from double-digit [property tax] millage again,'' Hardiman told me two years ago.

This qualifies.