What is {population} of {Washington, D.C.} that is {point in time} is {1860-1-1} ?
What was the census of Washington, D.C. in the beginning of 1860?
What was the population of Washington, D.C. at the start of 1860?
SELECT ?y WHERE { ?t property:point_in_time ?y . ?t property:population ?y . FILTER ( CONTAINS ( YEAR ( ?y ) , '1860' ) ) . resource:Washington,_D.C. property:population ?t }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q61> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1082> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P585> <1860-1-1>
} 

SELECT ?obj WHERE { wd:Q61 p:P1082 ?s . ?s ps:P1082 ?obj . ?s pq:P585 ?x filter(contains(YEAR(?x),'1860')) }