Saturday night's outage stalled two trams holding about 40 people each and another 100 were trapped at the top of the stainless steel monument, The St. Louis Post-Dispatch reported Sunday.
There were no reports of injuries and people remained calm.
It took about two hours to get everyone downstairs and then through the north tram, which resumed operation late Saturday and was open for business Sunday. The south tram remained closed Sunday.
The monument, operated by the National Park Service, has been one of the region's most popular attractions since it opened in 1966.
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