Hi Ruth, If Orlando and Louisa had another child, he/she didn't live long. In 1850 the family was living in Defiance, Defiance Co., Ohio. Orlando Evans, b. OH, 32, merchant Louisa A., wife, b. OH, 27. Mary E., dau, b. OH, 2. Julia Black, 30. Harriet Woodward, b. OH, 25. [Census doesn't say but probably Louisa's sister.]
In 1860 the family was living in Bridgeport, Nevada Co., CA. Orlando Evans, b. OH, 43, miner. Louisa, wife, b. OH, 39. Mary L., b. OH, 12. John Miller, servant. Avard Braner, miner.
You found them in the 1870 Census and I couldn't find them in the 1880 Census.
In 1875 Orlando, Louisa and Rebecca Pryor are living in Washoe Co., Nevada.
Orlando died 20 Aug 1887, Reno, Washoe Co., NV. Source: Smith-Evans-Sanders-Ittner Family Tree, trees.ancestry.com/tree,26479408/person/12207563657.
They also list Louisa's maiden name as Woodward and only one daughter Mary. Successful Searching!
Orlando Evans died 20 Aug 1887, Reno, WAshoe Co., Nevada.