I am looking for the marriage of Allan Winfred Henderson to Barbara Louise Robertson. Allan was born in London on 24 May 1899, and served in the British Army. In 1943 he arrived at St Albans, Vermont, on his way to take up a post with the British Army Staff in Washington DC. There is another record of him arriving at the Port of New York on 28 December 1950, which gives his last residence as Washington DC, his address as 3925 Benton St NW, and his next of kin as his wife Barbara, at the same address. It also says he had previously been in the US from June 1943 until 26 December 1950, which is just 2 days before this immigration record. (I don't know what to make of this either!)
According to a stone in the Masonic Memorial Gardens, Reno, Nevada Allan died in 1990 and Barbara Louise was born 1908 and died 1997. Family lore says that Barbara's surname was Robertson.
I have not found any record of his marriage in England, Scotland or Wales, so I am wondering if perhaps Barbara was a US citizen and they were married in Washington DC. However I don't know which state to look in for a marriage in Washington DC.
The Nevada birth and death records on Family Search only go to 1992, and they don't include Washoe County, which is where I gather Reno is, so I can't expect to find any information there about Barbara.