Only the 1st Tuesday of every month is free. Otherwise, the Museum is free for L.A. residents with proof of address every day from 3pm to 5pm. Please refer to our official site for more information: https://nhm.org/plan-your-visit
If you are a resident of Los Angeles and have an ID that shows your zip code, entry is free after 3 p.m. everyday. And I think that children under 11 enter free regardless of the schedule
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