A PO BOX number can be less than or more than four digit. For post office boxes, the general rule is that each box has its own ZIP+4 code.
The last four digit is often one of the following:
1. Zero plus the last three digits of the box number (eg. PO BOX 1001, Los Angeles CA 90001-0001).
2. The last four digits of the box number (eg. PO BOX 9991, Twin Peaks CA 92391-9991).
3. If the box number is less than four digits, enough zeros prepended to the front of the box number to produce a four-digit number(eg. PO BOX 1, Shreveport LA 71161-0001).
However, there is no uniform rule, the zip code plus four is for reference only, the ZIP+4 code must be looked up individually for each box in the USPS offical website.
PO BOX 1211, SPENCER, IA 51301-1211
PO BOX 1212, SPENCER, IA 51301-1212
PO BOX 1213, SPENCER, IA 51301-1213
PO BOX 1214, SPENCER, IA 51301-1214
PO BOX 1215, SPENCER, IA 51301-1215
PO BOX 1216, SPENCER, IA 51301-1216
PO BOX 1217, SPENCER, IA 51301-1217
PO BOX 1218, SPENCER, IA 51301-1218
PO BOX 1219, SPENCER, IA 51301-1219
PO BOX 1220, SPENCER, IA 51301-1220
PO BOX 1221, SPENCER, IA 51301-1221
PO BOX 1222, SPENCER, IA 51301-1222
PO BOX 1223, SPENCER, IA 51301-1223
PO BOX 1224, SPENCER, IA 51301-1224
PO BOX 1225, SPENCER, IA 51301-1225
PO BOX 1226, SPENCER, IA 51301-1226
PO BOX 1227, SPENCER, IA 51301-1227
PO BOX 1228, SPENCER, IA 51301-1228
PO BOX 1229, SPENCER, IA 51301-1229
PO BOX 1230, SPENCER, IA 51301-1230
PO BOX 1231, SPENCER, IA 51301-1231
PO BOX 1232, SPENCER, IA 51301-1232
PO BOX 1233, SPENCER, IA 51301-1233
PO BOX 1234, SPENCER, IA 51301-1234
PO BOX 1235, SPENCER, IA 51301-1235
PO BOX 1236, SPENCER, IA 51301-1236
PO BOX 1237, SPENCER, IA 51301-1237
PO BOX 1238, SPENCER, IA 51301-1238
PO BOX 1239, SPENCER, IA 51301-1239
PO BOX 1240, SPENCER, IA 51301-1240
PO BOX 1241, SPENCER, IA 51301-1241
PO BOX 1242, SPENCER, IA 51301-1242
PO BOX 1243, SPENCER, IA 51301-1243
PO BOX 1244, SPENCER, IA 51301-1244
PO BOX 1245, SPENCER, IA 51301-1245
PO BOX 1246, SPENCER, IA 51301-1246
PO BOX 1247, SPENCER, IA 51301-1247
PO BOX 1248, SPENCER, IA 51301-1248
PO BOX 1249, SPENCER, IA 51301-1249
PO BOX 1250, SPENCER, IA 51301-1250
PO BOX 1251, SPENCER, IA 51301-1251
PO BOX 1252, SPENCER, IA 51301-1252
PO BOX 1253, SPENCER, IA 51301-1253
PO BOX 1254, SPENCER, IA 51301-1254
PO BOX 1255, SPENCER, IA 51301-1255
PO BOX 1256, SPENCER, IA 51301-1256
PO BOX 1257, SPENCER, IA 51301-1257
PO BOX 1258, SPENCER, IA 51301-1258
PO BOX 1259, SPENCER, IA 51301-1259
PO BOX 1260, SPENCER, IA 51301-1260
PO BOX 1261, SPENCER, IA 51301-1261
PO BOX 1262, SPENCER, IA 51301-1262
PO BOX 1263, SPENCER, IA 51301-1263
PO BOX 1264, SPENCER, IA 51301-1264
PO BOX 1265, SPENCER, IA 51301-1265
PO BOX 1266, SPENCER, IA 51301-1266
PO BOX 1267, SPENCER, IA 51301-1267
PO BOX 1268, SPENCER, IA 51301-1268
PO BOX 1269, SPENCER, IA 51301-1269
PO BOX 1270, SPENCER, IA 51301-1270
PO BOX 1271, SPENCER, IA 51301-1271
PO BOX 1272, SPENCER, IA 51301-1272
PO BOX 1273, SPENCER, IA 51301-1273
PO BOX 1274, SPENCER, IA 51301-1274
PO BOX 1275, SPENCER, IA 51301-1275
PO BOX 1276, SPENCER, IA 51301-1276
PO BOX 1277, SPENCER, IA 51301-1277
PO BOX 1278, SPENCER, IA 51301-1278
PO BOX 1279, SPENCER, IA 51301-1279
PO BOX 1280, SPENCER, IA 51301-1280
PO BOX 1281, SPENCER, IA 51301-1281
PO BOX 1282, SPENCER, IA 51301-1282
PO BOX 1283, SPENCER, IA 51301-1283
PO BOX 1284, SPENCER, IA 51301-1284
PO BOX 1285, SPENCER, IA 51301-1285
PO BOX 1286, SPENCER, IA 51301-1286
PO BOX 1287, SPENCER, IA 51301-1287
PO BOX 1288, SPENCER, IA 51301-1288
PO BOX 1289, SPENCER, IA 51301-1289
PO BOX 1290, SPENCER, IA 51301-1290
PO BOX 1291, SPENCER, IA 51301-1291
PO BOX 1292, SPENCER, IA 51301-1292
PO BOX 1293, SPENCER, IA 51301-1293
PO BOX 1294, SPENCER, IA 51301-1294
PO BOX 1295, SPENCER, IA 51301-1295
PO BOX 1296, SPENCER, IA 51301-1296
PO BOX 1297, SPENCER, IA 51301-1297
PO BOX 1298, SPENCER, IA 51301-1298
PO BOX 1299, SPENCER, IA 51301-1299
PO BOX 1300, SPENCER, IA 51301-1300
PO BOX 1301, SPENCER, IA 51301-1301
PO BOX 1302, SPENCER, IA 51301-1302
PO BOX 1303, SPENCER, IA 51301-1303
PO BOX 1304, SPENCER, IA 51301-1304
PO BOX 1305, SPENCER, IA 51301-1305
PO BOX 1306, SPENCER, IA 51301-1306
PO BOX 1307, SPENCER, IA 51301-1307
PO BOX 1308, SPENCER, IA 51301-1308
PO BOX 1309, SPENCER, IA 51301-1309
PO BOX 1310, SPENCER, IA 51301-1310
PO BOX 1311, SPENCER, IA 51301-1311
PO BOX 1312, SPENCER, IA 51301-1312
PO BOX 1313, SPENCER, IA 51301-1313
PO BOX 1314, SPENCER, IA 51301-1314
PO BOX 1315, SPENCER, IA 51301-1315
PO BOX 1316, SPENCER, IA 51301-1316
PO BOX 1317, SPENCER, IA 51301-1317
PO BOX 1318, SPENCER, IA 51301-1318
PO BOX 1319, SPENCER, IA 51301-1319
PO BOX 1320, SPENCER, IA 51301-1320
PO BOX 1321, SPENCER, IA 51301-1321
PO BOX 1322, SPENCER, IA 51301-1322
PO BOX 1323, SPENCER, IA 51301-1323
PO BOX 1324, SPENCER, IA 51301-1324
PO BOX 1325, SPENCER, IA 51301-1325
PO BOX 1326, SPENCER, IA 51301-1326
PO BOX 1327, SPENCER, IA 51301-1327
PO BOX 1328, SPENCER, IA 51301-1328
PO BOX 1329, SPENCER, IA 51301-1329
PO BOX 1330, SPENCER, IA 51301-1330
PO BOX 1331, SPENCER, IA 51301-1331
PO BOX 1332, SPENCER, IA 51301-1332
PO BOX 1333, SPENCER, IA 51301-1333
PO BOX 1334, SPENCER, IA 51301-1334
PO BOX 1335, SPENCER, IA 51301-1335
PO BOX 1336, SPENCER, IA 51301-1336
PO BOX 1337, SPENCER, IA 51301-1337
PO BOX 1338, SPENCER, IA 51301-1338
PO BOX 1339, SPENCER, IA 51301-1339
PO BOX 1340, SPENCER, IA 51301-1340
PO BOX 1341, SPENCER, IA 51301-1341
PO BOX 1342, SPENCER, IA 51301-1342
PO BOX 1343, SPENCER, IA 51301-1343
PO BOX 1344, SPENCER, IA 51301-1344
PO BOX 1345, SPENCER, IA 51301-1345
PO BOX 1346, SPENCER, IA 51301-1346
PO BOX 1347, SPENCER, IA 51301-1347
PO BOX 1348, SPENCER, IA 51301-1348
PO BOX 1349, SPENCER, IA 51301-1349
PO BOX 1350, SPENCER, IA 51301-1350
PO BOX 1351, SPENCER, IA 51301-1351
PO BOX 1352, SPENCER, IA 51301-1352
PO BOX 1353, SPENCER, IA 51301-1353
PO BOX 1354, SPENCER, IA 51301-1354
PO BOX 1355, SPENCER, IA 51301-1355
PO BOX 1356, SPENCER, IA 51301-1356
PO BOX 1357, SPENCER, IA 51301-1357
PO BOX 1358, SPENCER, IA 51301-1358
PO BOX 1359, SPENCER, IA 51301-1359
PO BOX 1360, SPENCER, IA 51301-1360
PO BOX 1361, SPENCER, IA 51301-1361
PO BOX 1362, SPENCER, IA 51301-1362
PO BOX 1363, SPENCER, IA 51301-1363
PO BOX 1364, SPENCER, IA 51301-1364
PO BOX 1365, SPENCER, IA 51301-1365
PO BOX 1366, SPENCER, IA 51301-1366
PO BOX 1367, SPENCER, IA 51301-1367
PO BOX 1368, SPENCER, IA 51301-1368
PO BOX 1369, SPENCER, IA 51301-1369
PO BOX 1370, SPENCER, IA 51301-1370
PO BOX 1371, SPENCER, IA 51301-1371
PO BOX 1372, SPENCER, IA 51301-1372
PO BOX 1373, SPENCER, IA 51301-1373
PO BOX 1374, SPENCER, IA 51301-1374
PO BOX 1375, SPENCER, IA 51301-1375
PO BOX 1376, SPENCER, IA 51301-1376
PO BOX 1377, SPENCER, IA 51301-1377
PO BOX 1378, SPENCER, IA 51301-1378
PO BOX 1379, SPENCER, IA 51301-1379
PO BOX 1380, SPENCER, IA 51301-1380
PO BOX 1381, SPENCER, IA 51301-1381
PO BOX 1382, SPENCER, IA 51301-1382
PO BOX 1383, SPENCER, IA 51301-1383
PO BOX 1384, SPENCER, IA 51301-1384
PO BOX 1385, SPENCER, IA 51301-1385
PO BOX 1386, SPENCER, IA 51301-1386
PO BOX 1387, SPENCER, IA 51301-1387
PO BOX 1388, SPENCER, IA 51301-1388
PO BOX 1389, SPENCER, IA 51301-1389
PO BOX 1390, SPENCER, IA 51301-1390
PO BOX 1391, SPENCER, IA 51301-1391
PO BOX 1392, SPENCER, IA 51301-1392
PO BOX 1393, SPENCER, IA 51301-1393
PO BOX 1394, SPENCER, IA 51301-1394
PO BOX 1395, SPENCER, IA 51301-1395
PO BOX 1396, SPENCER, IA 51301-1396
PO BOX 1397, SPENCER, IA 51301-1397
PO BOX 1398, SPENCER, IA 51301-1398
PO BOX 1399, SPENCER, IA 51301-1399
PO BOX 1400, SPENCER, IA 51301-1400
PO BOX 1401, SPENCER, IA 51301-1401
PO BOX 1402, SPENCER, IA 51301-1402
PO BOX 1403, SPENCER, IA 51301-1403
PO BOX 1404, SPENCER, IA 51301-1404
PO BOX 1405, SPENCER, IA 51301-1405
PO BOX 1406, SPENCER, IA 51301-1406
PO BOX 1407, SPENCER, IA 51301-1407
PO BOX 1408, SPENCER, IA 51301-1408
PO BOX 1409, SPENCER, IA 51301-1409
PO BOX 1410, SPENCER, IA 51301-1410
PO BOX 1411, SPENCER, IA 51301-1411