America, make room for Kiyah Lanae Boyd, 6 pounds, 6 ounces, and Zoe Emille Hudson, 7 pounds, 3 ounces – both of whom arrived Tuesday morning as instant contenders for the symbolic title of 300 millionth American.

At 7:45 a.m. and about 30 seconds, the U.S. Population Clock, located at the Census Bureau’s headquarters in the Washington suburb of Suitland, Md., turned from 299,999,999 to 300,000,000. Within seconds, at 7:46 a.m., Kiyah was delivered at Northside Hospital in Atlanta and Zoe came into the world at New York Presbyterian Hospital in Manhattan.

In Atlanta, parents Keisha and Petty Officer 1st Class Kristopher Boyd, both 28, are African-American. Dad is home on two weeks’ leave from Bahrain for his daughter’s birth; the family lives in Mableton, a Cobb County community just outside Atlanta. Little Kiyah has a brother, Keyon’dre, who will be 2 at the end of the month.

Zoe’s mother, Maria Diaz, and father, Gavin Hudson – 28 and 29, respectively – are both New York-born. But Diaz’s family is originally from Puerto Rico and the Dominican Republic, while Hudson’s family is from Jamaica. They live in Monroe, N.Y., a small town 47 miles north of the city. Hudson is an investment banker and Diaz is on leave from her job as a fourth-grade teacher in Harlem. They have two older daughters, Alexis, 9, and Brianna, 7.

In Suitland, a passel of Census officials and employees gathered by dawn’s early light in a lobby of the bureau’s new headquarters. At what amounted to demography’s Times Square, they counted down the last few ticks on the clock, which at its current setting (adjusted monthly) adds one person every 11 seconds. A bank of television cameras brought the event live to the nation and the world. When the milestone arrived, the crowd burst into applause, culminating weeks and months of buildup in the popular press (as Anderson Cooper posed it on his CNN show: “300 Million: Melting Pot Or Meltdown?”).

After all the anticipation, Census Bureau Director Charles Kincannon, on hand with his wife, was asked if he felt like he had given birth. He offered no comment.

But Howard Hogan, the bureau’s associate director for demographic programs, allowed that “when I became a demographer, I never thought it would be this exciting.”

There is, of course, no such thing as “the” 300 millionth American.

The moment chosen was based on Census Bureau estimates of population growth, the most recent calculations counting one birth every seven seconds, one death every 13 seconds, and one net migrant (immigrants minus emigrants) every 31 seconds. Even symbolically, the 300 millionth American could just as easily be a new immigrant landing at Kennedy Airport, swimming across the Rio Grande, stealing across the chilly Canadian border, or simply overstaying a student visa.