The greater Washington CSA comprises the Washington (blue), Baltimore (purple), and five smaller metropolitan or micropolitan areas. Image by the author.

Greater Washington may already be the country's third-most-populous region, according to new population projections from the Census Bureau. Under the bureau's broadest definition of a metropolitan area, called a "Combined Statistical Area," the Washington-Baltimore area was just shy of the Chicago region as of July 2017. Continued growth here means that this region's population may have recently surpassed Chicago's.

Second City could become fifth

Chicago has long been known as "the second city," a nickname popularized by a snarky book written in 1952 — ironically, just as its 70-year reign as the nation's second most populous city was ending. The exploding population of metro Los Angeles pushed it to third by 1960, where it has remained ever since. Yet slackening international immigration and continuing domestic out-migration from the Midwest have slowed overall population growth.

Chicago extends to the horizon. Image by the author.

The new Census estimates put greater Washington's population as of July 1, 2017 at 9,764,315, and Chicagoland's population at 9,901,711. Yet the estimates show Chicagoland's population falling slightly each year since 2014, while greater Washington has added 70,000-80,000 residents per year. If these estimates are correct and if those trends continued, greater Washington's population would have surpassed Chicagoland's in August of 2018.

Chicago could fall further down the league tables by the 2020 Census. The San Francisco Bay Area, known in Census nomenclature as the San Jose-San Francisco-Oakland, CA CSA, was recently expanded to incorporate Modesto and Merced, two cities in the Central Valley that send many commuters into Silicon Valley.

This boundary expansion expanded the Bay Area CSA's population by 9%, putting it not far behind greater Washington's population. Since the Bay Area is growing even faster than greater Washington, it will also soon pass Chicagoland in population.

Oakland and San Francisco, viewed from the east. Image by the author.

Neither Washington-Baltimore nor San Jose-San Francisco will likely ever come close to dethroning #2 Los Angeles, which is about twice as populous as either.

CSA vs. MSA

Combined Statistical Areas extend across very large areas, and reflect the increased economic interdependence of neighboring areas. The Census currently defines the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area as comprising seven metropolitan or "micropolitan" areas. These, in turn, encompass 41 counties and independent cities in four states and the District.

The region spans from DC and Baltimore City east to Easton on the eastern shore of Maryland, north to Waynesboro in Pennsylvania (north of Camp David), northwest to Berkeley Springs, West Virginia, southwest to Shenandoah National Park and Lake Anna in Virginia, and southeast to St. Mary's City in Maryland.

Greater Washington CSA counties
District of Columbia Virginia Pennsylvania
Alexandria city Franklin
Maryland Arlington
Anne Arundel Clarke West Virginia
Baltimore Culpeper Berkeley
Baltimore city Fairfax Hampshire
Calvert Fairfax city Jefferson
Carroll Falls Church city Morgan
Charles Fauquier
Frederick Frederick
Harford Fredericksburg city
Howard Loudoun
Manassas city Madison
Montgomery Manassas city
Prince George's Manassas Park city
Queen Anne's Prince William
St. Mary's Rappahannock
Talbot Spotsylvania
Stafford
Warren
Winchester city

The boundaries of CSAs and MSAs are constantly changing, and are largely determined by commuter flows. If 15% of an area’s workers or employees commute to a different area, those areas are combined into a CSA.

Greater Washington extends far into the countryside beyond its core cities less because of supercommuters crossing multiple state lines (although they do exist), but rather because workers from Berkeley County, West Virginia might commute to Hagerstown, whose residents might commute to Frederick, whose workers commute to Montgomery County.

Polycentric region

The Los Angeles, Washington-Baltimore, and San Jose-San Francisco regions all have (or will soon have) larger populations and economies than Chicago. Yet the crowds and skyscrapers of Chicago's Loop certainly gives it more of a bustling big city feel than any of the other three regions.

The Lakeshore East neighborhood of Chicago. Image by the author.

The reason comes down, mostly, to timing: Chicago, like New York, boomed around 1900, when railroads were the primary means of travel and fed highly centralized downtown business districts. LA, Washington, and the Bay Area all came of age later in the 20th century, when widespread auto ownership led to much more dispersed urbanization. These "polycentric" regions have their populations and economies spread across multiple smaller centers, which each have individual specializations.

Some are larger than others, but they're deeply interlinked on a daily basis by cross-commuting. For instance, while downtown Chicago rivals the District in terms of office space and employment, the Maryland and Virginia suburbs have over twice as much office as Chicago's suburbs do.

Arlington's Ballston to Rosslyn corridor is one of many urban centers in greater Washington. Image by Arlington County licensed under Creative Commons.

That we'll grow is a given, but where we grow matters

The region's population will continue to grow; even if a wall were built to keep all new outsiders from moving in, greater Washington would still need to build hundreds of new homes every week, just to house the young people who were born and raised here. The policy decisions that are made today cannot say whether our region grows.

Instead, they can only direct where and how our region grows — decisions that matter tremendously for our region's economy, environment, and ability to improve equity. With better planning, a more populous Washington region can be a better region, offering even more opportunities for more people to live, work, and enjoy.