WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<RESTATED>
<CIK> 0000860953
<NAME> NUVEEN TAX-FREE UNIT TRUST
<SERIES> Series 622
<NAME> NEW YORK INSURED TRUST
<NUMBER> 170
<MULTIPLIER> 1
<CURRENCY> U.S. DOLLARS
<FISCAL-YEAR-END> JUL-31-2000
<PERIOD-START> AUG-01-1999
<PERIOD-END> JUL-31-2000
<PERIOD-TYPE> YEAR
<EXCHANGE-RATE> 1
<INVESTMENTS-AT-COST> 4,529,990
<INVESTMENTS-AT-VALUE> 4,738,761
<RECEIVABLES> 76,110
<ASSETS-OTHER> 28,931
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 4,843,802
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 5,940
<TOTAL-LIABILITIES> 5,940
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 0
<SHARES-COMMON-STOCK> 49,129
<SHARES-COMMON-PRIOR> 51,306
<ACCUMULATED-NII-CURRENT> 65,163
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 141,841
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 208,771
<NET-ASSETS> 4,837,862
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 336,888
<OTHER-INCOME> 0
<EXPENSES-NET> 6,803
<NET-INVESTMENT-INCOME> 330,085
<REALIZED-GAINS-CURRENT> -5,888
<APPREC-INCREASE-CURRENT> -100,462
<NET-CHANGE-FROM-OPS> 223,735
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 360,504
<DISTRIBUTIONS-OF-GAINS> 267,179
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 70,000
<NUMBER-OF-SHARES-REDEEMED> 20,871
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> -619,635
<ACCUMULATED-NII-PRIOR> 95,584
<ACCUMULATED-GAINS-PRIOR> 147,728
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 0
<AVERAGE-NET-ASSETS> 0
<PER-SHARE-NAV-BEGIN> 0
<PER-SHARE-NII> 0
<PER-SHARE-GAIN-APPREC> 0
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 0
<EXPENSE-RATIO> 0
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0
</TABLE>