  We have recovered the sunspot observations made by David E. Hadden during
1890-1931 from Alta, Iowa. We have digitized the available data published by
Hadden in different astronomical journals. This data series have been analyzed
and compared with the standard sunspot number series. Moreover, we provide
additional information on two great sunspot groups, previously not described,
that originated two important extreme episodes of space weather on February
1892 and September 1898.
