There are good populations of Spring Beauty at Great Falls Park in northern VA and also across the Potomac in the Carderock area of the C & O Canal in MD. I'm sure there are other parks in the Washington area which have good populations as well. You might check "Finding Wildflowers in the Baltimore Washington Area" by Cris Fleming and Marion Lobstein for additional locations. This is a little more than an hour away from Catoctin Mountain Park which Becky recommends.
I'm also curious why you call Andrena erigeniae, a specialist pollinator of Spring Beauty. It's specific name would imply that it pollinates Harbinger of Spring (Erigenia bulbosa) which blooms over a much shorter period and earlier than Spring Beauty (Claytonia virginica). Harbinger of Spring can be found at the two parks I've mentioned above and they are sometimes associated with Spring Beauty but Spring Beauty blooms over a much longer period and usually starts a little later.
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