This was shared on the Yankee Clipper Contest Club email list on May 26, 2021, by Ray Conrad NM2O. Reprinted here with his permission.

There are 930 possible USA Prefixes, that’s for continental and offshore. Some like KP1 or KP5 are not active now. The rarest are in Alaska where there is only one WL2 and two WL3 calls. If we back out about 48 offshore prefixes, it’s about 880 in the lower 48. Someone with WPX honor roll might know if a prefix like NP1 or WP1 was ever issued.

In most districts, there are at least 22 calls assigned in each prefix where it’s mostly 2×1.

Some prefixes have thousands of calls where it can have 2×1, 2×2 and 2×3. KA1 has 5204 hits.

There is turnover, many times a 2×1 is turned in for a 1×2. The AE7Q site shows the available calls and application status.

QRZ allows searching with an *.  So, AA1* shows that there are 664 hits. The “alias match” shows previous calls. For example, W1CLW turned in AA1XH. So, the exact number would need to be determined from the current FCC database.

The following is the continental USA prefixes worked by TI7W last year in WPX CW 2020. He had 436 USA out of his total of 1135 prefixes. (AH2 is an exception, he doesn’t sign “portable.”)

Here’s the list as tabulated by the SH5 analysis program.

Formatting the results as a table allows the holes to be seen. Can you borrow a call and fill in a slot?

AA0 AA1 AA2 AA3 AA4 AA5 AA6 AA7 AA8 AA9 
AB0 AB1 AB2 AB3 AB4         AB7     AB9 
AC0 AC1             AC5 AC6 AC7     AC9 
AD0 AD1     AD3 AD4 AD5 AD6 AD7 AD8 AD9 
AE0 AE1 AE2 AE3 AE4 AE5 AE6 
            AF3 AF4 AF5 AF6 AF7 AF8 
            AG3         AG6         AG9 
    AI1 AI2     AI4                 AI9 
    AJ1     AJ3         AJ6     AJ8 AJ9 
    AK1 AK2             AK6         AK9 
K0  K1  K2  K3  K4  K5  K6  K7  K8  K9 
KA0 KA1 KA2 KA3 KA4 KA5 KA6     KA8 KA9 
    KB1 KB2 KB3 KB4 KB5 KB6 KB7 KB8 KB9 
        KC2 KC3 KC4 KC5     KC7 KC8 KC9 
KD0     KD2 KD3 KD4 KD5 KD6 KD7 KD8 
KE0 KE1 KE2 KE3 KE4 KE5 KE6         KE9 
        KF2 KF3     KF5     KF7 
KG0 KG1     KG3 KG4 KG5 KG6 KG7     KG9 
KI0             KI4 KI5 KI6 KI7 KI8 
KJ0             KJ4 KJ5 KJ6 
            KK3 KK4 KK5     KK7     KK9 
KM0 KM1     KM3 KM4 KM5 KM6 KM7     KM9 
KN0 KN1         KN4 KN5 KN6 KN7 
            KO3 KO4     KO6     KO8 
    KQ1         KQ4 KQ5 
        KR2     KR4     KR6 KR7 KR8 
KS0     KS2 KS3 KS4         KS7     KS9 
KT0 KT1     KT3 KT4 KT5 KT6 KT7 KT8 KT9 
KU0 KU1 KU2             KU6 KU7 KU8 KU9 
KV0 KV2 KV3             KV6     KV8 
KW0 KW1          KW4        KW7 
KX0 KX1 KX2                 KX7     KX9 
KY0     KY2             KY6 KY7 
    KZ1             KZ5     KZ7 KZ8 KZ9 
N0  N1  N2  N3  N4  N5  N6  N7  N8  N9 
            NA3 NA4 NA5 NA6     NA8 NA9 
    NB1     NB3 NB4     NB6 
    NC1     NC3         NC6 NC7 NC8 
        ND2 ND3 ND4         ND7     ND9 
NE0 NE1     NE3 NE4 NE5 NE6 NE7 NE8 NE9 
                NF4 NF5 NF6     NF8 
    NG1     NG3         NG6 NG7 
NI0 NI1                     NI7 
    NJ1 NJ2 NJ3         NJ6     NJ8 
                NK4 NK5 NK6     NK8 NK9 
    NM1         NM4 NM5 NM6     NM8 
    NN1 NN2 NN3 NN4 NN5 NN6 NN7 
            NO3         NO6 
        NQ2         NQ5             NQ9 
NR0 NR1     NR3 NR4 NR5 NR6 NR7  
        NS2     NS4             NS8 NS9 
NT0                 NT5 NT6 NT7 
                NU4 NU5 NU6 NU7 NV8 
    NW1 NW2 NW3         NW6 NW7 
NX0         NX3 NX4     NX6     NX8 
            NY3 NY4     NY6 NY7 NY8 
        NZ2     NZ4     NZ6 NZ7 
W0  W1  W2  W3  W4  W5  W6  W7  W8  W9 
WA0 WA1 WA2 WA3 WA4 WA5 WA6 WA7 WA8 WA9 
WB0     WB2     WB4 WB5 WB6 WB7 WB8 WB9 
WC0         WC3     WC5 WC6 WC7 
WD0                             WD8 WD9 
WE0     WE2         WE5 WE6     WE8 WE9 
            WF3             WF7     WF9 
            WG3     WG5             WG9 
                        WI6 WI7 
    WJ1 WJ2     WJ4 WJ5             WJ9 
WK0 WK1 WK2     WK4 WK5 WK6 WK7 
            WM3                     WM9 
    WN1 WN2 WN3 WN4     WN6 WN7 
    WO1 WO2 WO3 WO4     WO6 WO7 
                    WQ5 WQ6 
    WR1 WR2 WR3 WR4         WR7 
            WS3 WS4     WS6 WS7     WS9 
        WT2                     WT8 WT9 
                        WU6         WU9 
                WV4         WV7 
    WW1 WW2     WW4 WW5 
            WX3     WX5 WX6     WX8 
            WY3                 WY8 
                            WZ7 WZ8