@Homegrwoninillinois It’s a type of raspberry that’s 5/8 inches in diameter, firm, hardy, and productive but with mediocre flavor. It took 30 years to develop in the 1800s. From Marlboro, Ulster County, NY. Bred by Andrew J Caywood of Marlboro, New York. As far as I know, it's not smooth and mild and refreshingly addictive.
However, it does seem like it was well-marketed. Subscribers to various horticultural publications were able to get free plants in the 1880s.
According to “The Cultivator & Country Gentleman” July 31, 1884: “The Marlboro Raspberry — Has been largely advertised, and much interest has been felt as to the claims for real value. Having had another year for examination, we are induced to award to it much real merit in localities where it succeeds. A correspondent in the raspberry region in Ulster county, says it appears to be “up to expectation, except in earliness, being later than Highland Hardy, Hansell and Lost Rubies, and it will rival, and probably take the place of Cuthbert, being lighter in color, harder, holding its color longer, and is just as thrifty and healthy, and is quite as productive. I find no rival Highland Hardy in earliness, productiveness or profit. ’Superb’ breaks all to pieces. Lost Rubies, if picked daily, or every two days, is profitable.” H. S. Anderson of Union Springs, N.Y., has (in addition to some thousands of young plants of the Marlboro) a hundred or two in full bearing, an examination of which shows its vigor, hardiness and productiveness. the berries measure five eighths of an inch in diameter, some of them three-fourths, or about the size of Clarke, but more rounded. They are quite firm in texture, red in color, and begin to ripen at Union Springs about the first of July. Although quite moderate in flavor, the Marlboro promises to be a valuable market sort. In some locations it is reported as a partial failure, showing the importance of giving it a trial in different places before pronouncing on its value for general cultivation."
Who knew that "raspberry correspondent" used to be a real job?!
Excerpt from "The Annals of Horticulture In North America for the year 1889":
ANDREW J. CAYWOOD. BY W. C. CAYWOOD. Andrew J. Caywood was borne in Orange County, NewYork, in August, 1819, and died at Marlboro, N. Y., Jan. 13th, 1889. He was the youngest of eight children. His father, who was a farmer, died when he was quite young. He continued at farming until 22 or 23 years of age, when feeling the need of a better education than his former opportunities had afforded, he attended the Amenia (N. Y.) Seminary for two years, making special studies of botany and geology. At 27 years of age he married and bought a small farm in Ulster county and began the fruit and nursery business. He planted the first vineyards and peach orchards for market purposes in Ulster county, and by his enthusiasm induced neighbors to do like-wise; and principally through his efforts, Ulster county is now the foremost fruit producing section in the east. At the same time he commenced the crossing of fruits and planting the seeds, with a view of improving on existing varieties, and to this branch he devoted most of his energy and means for the balance of his life, each year having thousands of seedings to discard after cultivating and watching them for from three to six years. From the first planting of the seed he was thirty years in producing the Marlboro raspberry by crossing and re-crossing the seedlings of six generations. The named fruits he has originated are the Walter, Modena, Hudson, Duchess, Lily, Ulster, Poughkeepsie, WhiteConcord, Nectar and Metternich grapes ; Cetywayo and Mammoth Bush strawberries, Marlboro and Crystal raspberries, and Minnewaska blackberry, besides some eighty varieties of grapes, raspberries, currants, pears, cherries, etc., which are numbered, many of which give promise of much value. He always selected the best of native varieties for his experiments, never intermixing any foreign blood, as he believed that only pure natives could withstand the diversities of our climate.All of the fruits he has disseminated are the best of their class, and although he did not accumulate riches, he has left something which will last longer, and keep him in memory of all who enjoy one of nature's best gifts—good fruit.