I was reading SkyscraperCity and found this very interesting.

Daytime Population

500,000+
Albuquerque, New Mexico 566,581
Atlanta, Georgia 687,251
Austin, Texas 911,073
Baltimore, Maryland 723,951
Boston, Massachusetts 844,309
Charlotte, North Carolina 835,219
Chicago, Illinois 2,880,923
Cleveland, Ohio 530,092
Columbus, Ohio 850,506
Dallas, Texas 1,430,898
Denver, Colorado 734,217
Detroit, Michigan 808,908
El Paso, Texas 635,959
Fort Worth, Texas 763,796
Fresno, California 522,211
Houston, Texas 2,645,327!
Indianapolis, Indiana 949,227
Jacksonville, Florida 887,380
Kansas City, Missouri 545,534
Las Vegas, Nevada 630,339
Los Angeles, California 3,942,579
Louisville, Kentucky 644,192
Memphis, Tennessee 771,573
Miami, Florida 605,034
Milwaukee, Wisconsin 620,609
Nashville, Tennessee 689,904
New York, New York 8,687,425
Oklahoma City, Oklahoma 658,914
Philadelphia, Pennsylvania 1,611,196
Phoenix, Arizona 1,582,418
Portland, Oregon 688,575
Sacramento, California 563,495
San Antonio, Texas 1,393,160
San Diego, California 1,449,880
San Francisco, California 951,627
San Jose, California 874,886
San Juan, Puerto Rico 511,974
Seattle, Washington 752,827
Tucson, Arizona 573,581
Washington, District of Columbia 1,046,036

current and traditional peer cities highlighted. OKC central city adds nearly 60,000 net each day. DC nearly doubles.