This article is co-authored by Will Creasy, a geospatial analyst at Urban3.

A few months ago, Chuck Marohn wrote an article asking when it's okay to annex property, and it struck a nerve in the Urban3 office.

As Chuck explained, “Annexation — the act of bringing property outside of the city limits into the municipal boundaries—is rarely more than an economic sugar high for a city, one with long-term consequences that are nearly always negative.”

If you want your city to grow in a financially healthy, productive way, it takes discipline and a balanced diet. But if you only seek that sugar high when you’re hungry, you’ll grow, alright—but in a manner that will leave you bloated and unsatisfied.

Annexation is effectively a release valve for the city, and it’s natural. Every growing city has to expand its boundaries at some point. In fact, 90% of cities that could annex additional land in the 1990’s did so. At Urban3, we were most curious about why, where, and when cities annex land.

Chuck pointed out that “a common (incorrect) argument that city staff often put forth when they recommend annexations goes something like this: we already have a fire department, a police department, a library and parks….why not have more taxpayers sharing those costs?”

Another argument is that if workers are moving outside the city, why not move city boundaries outward so they still pay for services? The answer is that annexation is almost always a poor investment that doesn’t consider long term stability. Simply put, annexation is a bailout. So what’s the difference between natural growth and a sugar high? Where do we draw the line?

There are many explanations for the placement of city boundaries, the most obvious of which is geography. In Boulder, the city limits directly abut the Rocky Mountains, so that’s a sensible place to draw the line. Some city boundaries can be drawn across cultural or political lines, but those can seem absurd in situations like where the Missouri River splits Kansas City in two across state lines. In situations where geography isn’t a factor, who’s to say that someone just over the border of a city’s official boundaries is not a citizen, but their next-door neighbor is?

Annexation Around the Country

We at Urban3 analyzed the annexation patterns of dozens of cities, and it turns out that the closer you look, the more you discover that annexation shows a city’s priorities in clear detail. Here are a few examples: