The Skidmore family is not in any danger of extinction. In the United States there are almost 4000 heads of households named Skidmore (including the less common spellings of Scudamore, Scidmore and Sidmore) with listed telephone numbers. Most of these are descended (on the basis of the 1920 census) from Thomas Skidmore (Scudamore) who came from Westerleigh, Gloucestershire to Boston, Massachusetts by 1636. A considerably smaller family descends from the brothers Henry and Thomas Skidmore, once of Rickmansworth, Hertfordshire who came together to Kent County, Delaware in 1668. There has been (according to a fairly recent count) 15,214 persons named Skidmore in the United States who have registered for Social Security cards down through the years, some of them descended from more recent immigrants.
In England, an exact count in the 1985 telephone books found fewer than 1500 Skidmores or Scudamores. About half of the surviving branches in England (and America) descend from a branch founded by a William Skudemore who married in 1625 at Kingswinford, Staffordshire. Looking at Australia and Canada, which are more sparsely populated, only 113 and 187 households were found with telephones in the same period.
The largest body of Scudamore/Skidmore research will be found on the Scudamore/Skidmore Family History CD published in 2006. It includes copies of over 20,000 pages of notes amassed over the last 50 years by Warren Skidmore and clipped into several hundred loose-leaf notebooks. The British notes, about a quarter of the whole, is fairly complete down to the time of the Commonwealth. The American family has been continued down to roughly 1900 in the interest of economy. Later information on both sides of the Atlantic is frequently more or less proportional to the interest shown in the individual branches that have living descendants. The CD is fully machine searchable for both names and places.
About five years ago William F. Skidmore (who produced the CD) began an intensive effort to identify and group different branches of the family using DNA. See the DNA Surname Project link for more information.