I think the list the OP uses is fundamentally flawed because it’s based on the population of the central city only, making no allowances for the rest of the urbanized area an outsider would still consider to be part of “Greater Wherever, USA”. As a result, some larger urban areas with unusually small core cities are left off, and other smaller areas with unusually large core cities are included.
This is a list of the 97 urban areas in the US with >500,000 population.
# Location 2007 population
1 New York-Newark-Bridgeport, NY-NJ-CT-PA CSA 21,961,994
2 Los Angeles-Long Beach-Riverside, CA CSA 17,755,322
3 Chicago-Naperville-Michigan City, IL-IN-WI CSA 9,745,165
4 Washington-Baltimore-Northern Virginia, DC-MD-VA-WV CSA 8,241,912
5 Boston-Worcester-Manchester, MA-RI-NH CSA 7,476,689
6 San Jose-San Francisco-Oakland, CA CSA 7,264,887
7 Dallas-Fort Worth, TX CSA 6,498,410
8 Philadelphia-Camden-Vineland, PA-NJ-DE-MD CSA 6,385,461
9 Houston-Baytown-Huntsville, TX CSA 5,729,027
10 Atlanta-Sandy Springs-Gainesville, GA-AL CSA 5,626,400
11 Miami-Fort Lauderdale-Pompano Beach, FL MSA 5,413,212
12 Detroit-Warren-Flint, MI CSA 5,405,918
13 Phoenix-Mesa-Scottsdale, AZ MSA 4,179,427
14 Seattle-Tacoma-Olympia, WA CSA 4,038,741
15 Minneapolis-St. Paul-St. Cloud, MN-WI CSA 3,538,781
16 Denver-Aurora-Boulder, CO CSA 2,998,878
17 San Diego-Carlsbad-San Marcos, CA MSA 2,974,859
18 Cleveland-Akron-Elyria, OH CSA 2,896,968
19 St. Louis-St. Charles-Farmington, MO-IL CSA 2,866,517
20 Tampa-St. Petersburg-Clearwater, FL MSA 2,723,949
21 Orlando-Deltona-Daytona Beach, FL CSA 2,693,552
22 Pittsburgh-New Castle, PA CSA 2,446,703
23 Sacramento-Arden-Arcade-Yuba City, CA-NV CSA 2,397,691
24 Charlotte-Gastonia-Salisbury, NC-SC CSA 2,277,074
25 Cincinnati-Middletown-Wilmington, OH-KY-IN CSA 2,176,749
26 Portland-Vancouver-Beaverton, OR-WA MSA 2,175,113
27 Kansas City-Overland Park-Kansas City, MO-KS CSA 2,053,928
28 Indianapolis-Anderson-Columbus, IN CSA 2,014,267
29 San Antonio, TX MSA 1,990,675
30 Columbus-Marion-Chillicothe, OH CSA 1,982,252
31 Las Vegas-Paradise-Pahrump, NV CSA 1,880,449
32 Milwaukee-Racine-Waukesha, WI CSA 1,739,497
33 Salt Lake City-Ogden-Clearfield, UT CSA 1,686,703
34 Virginia Beach-Norfolk-Newport News, VA-NC MSA 1,658,754
35 Raleigh-Durham-Cary, NC CSA 1,635,974
36 Nashville-Davidson-Murfreesboro-Columbia, TN CSA 1,601,403
37 Austin-Round Rock, TX MSA 1,598,161
38 Greensboro-Winston-Salem-High Point, NC CSA 1,535,926
39 Louisville-Jefferson County-Elizabethtown-Scottsburg, KY-IN CSA 1,369,024
40 Grand Rapids-Muskegon-Holland, MI CSA 1,323,095
41 Hartford-West Hartford-Willimantic, CT CSA 1,306,151
42 Jacksonville, FL MSA 1,300,823
43 Memphis, TN-MS-AR MSA 1,280,533
44 Oklahoma City-Shawnee, OK CSA 1,262,027
45 Greenville-Spartanburg-Anderson, SC CSA 1,221,881
46 Richmond, VA MSA 1,212,977
47 Buffalo-Niagara-Cattaraugus, NY CSA 1,208,270
48 Birmingham-Hoover-Cullman, AL CSA 1,188,764
49 Albany-Schenectady-Amsterdam, NY CSA 1,148,416
50 Rochester-Batavia-Seneca Falls, NY CSA 1,122,845
51 New Orleans-Metairie-Bogalusa, LA CSA 1,075,283
52 Dayton-Springfield-Greenville, OH CSA 1,067,741
53 Fresno-Madera, CA CSA 1,045,861
54 Knoxville-Sevierville-La Follette, TN CSA 1,029,155
55 Tucson, AZ MSA 967,089
56 Tulsa-Bartlesville, OK CSA 955,643
57 Honolulu, HI MSA 905,601
58 Omaha-Council Bluffs-Fremont, NE-IA CSA 865,894
59 Little Rock-North Little Rock-Pine Bluff, AR CSA 841,326
60 Sarasota-Bradenton-Punta Gorda, FL CSA 839,995
61 Albuquerque, NM MSA 835,120
62 Allentown-Bethlehem-Easton, PA-NJ MSA 803,844
63 Baton Rouge-Pierre Part, LA CSA 793,028
64 Bakersfield, CA MSA 790,710
65 Columbia-Newberry, SC CSA 753,663
66 El Paso, TX MSA 734,669
67 Syracuse-Auburn, NY CSA 725,359
68 Toledo-Fremont, OH CSA 711,952
69 McAllen-Edinburg-Mission, TX MSA 710,514
70 Springfield, MA MSA 682,657
71 Youngstown-Warren-East Liverpool, OH-PA CSA 679,402
72 Chattanooga-Cleveland-Athens, TN-GA CSA 677,820
73 Stockton, CA MSA 670,990
74 Lexington-Fayette-Frankfort-Richmond, KY CSA 658,217
75 Harrisburg-Carlisle-Lebanon, PA CSA 656,781
76 Wichita-Winfield, KS CSA 630,703
77 Charleston-North Charleston-Summerville, SC MSA 630,100
78 Portland-Lewiston-South Portland, ME CSA 619,917
79 Des Moines-Newton-Pella, IA CSA 616,122
80 Madison-Baraboo, WI CSA 614,103
81 Colorado Springs, CO MSA 609,096
82 Cape Coral-Fort Myers, FL MSA 590,564
83 Boise City-Nampa, ID MSA 587,689
84 Mobile-Daphne-Fairhope, AL CSA 576,175
85 Lakeland-Winter Haven, FL MSA 574,746
86 Fort Wayne-Huntington-Auburn, IN CSA 570,779
87 South Bend-Elkhart-Mishawaka, IN-MI CSA 561,279
88 Jackson-Yazoo City, MS CSA 561,234
89 Scranton-Wilkes-Barre, PA MSA 549,430
90 Lafayette-Acadiana, LA CSA 538,470
91 Palm Bay-Melbourne-Titusville, FL MSA 536,161
92 Huntsville-Decatur, AL CSA 535,911
93 Port St. Lucie-Sebastian-Vero Beach, FL CSA 531,958
94 Augusta-Richmond County, GA-SC MSA 528,519
95 Lansing-East Lansing-Owosso, MI CSA 528,193
96 York-Hanover-Gettysburg, PA CSA 521,828
97 Modesto, CA MSA 511,263
Based from Statistical area (United States) - Wikipedia
The OP asked about which city is least-known. In my longer list any of those well down in the list would qualify.
Considering just the top 27 (the size of the OPs list), I’d say Charlotte or Kansas City have a pretty good shot at least-known.