Happy birthday, Chicago! Well, happy early birthday, anyway.

Saturday marks the 186th anniversary of Chicago’s founding as a city. As the candles on its birthday cake have grown with the passing years, so too have Chicago’s borders.

Here’s a look at how a once small-but-mighty city gobbled up surrounding land to become the City of the Big Shoulders (and expanded borders) that we know and love today.

On March 4, 1837, Chicago was incorporated as a city … of just 10 square miles.

That’s right, Chicago’s original borders were tight: Lake Michigan to Wood Street, 22nd Street to North Avenue. (Yeah, that’s why it’s called North Avenue.)

Today, Chicago is more than 230 square miles. So, how did the city of big shoulders get so, well, big?

Starting in the 1850s, Chicago began swallowing up surrounding land.

Not through conquest or anything — but mostly through the process of annexation, where suburban residents voted to become city dwellers.

The benefits went both ways. The townships got more municipal services, and the city got to expand its borders and population.

Hello, new taxable residents!

The biggest block of annexation happened in 1889, ahead of the Columbian Exposition. 

Hyde Park, Jefferson, Lake and Lake View townships voted to join Chicago — bringing with them a whopping 125 square miles and more than 200,000 residents.

But annexation wasn’t always smooth sailing.

Morgan Park’s 1911 annexation vote, overwhelmingly favored by women voters who weren’t yet allowed a voice in national elections, was held up in court for three years.

And that island of northwest suburbs stayed autonomous thanks to stubborn residents and skeptical Chicago politicians.

After decades of growth, Chicago eventually slowed its roll. The city started running into suburbs like Evanston and Oak Park with well-established identities of their own.

The last suburb to join the party was Mount Greenwood in 1927. And the last expansion was in 1956 when Chicago took over the land at O’Hare Airport. 

So that’s the story of Chicago’s start … and how the rest was won.