1858 San Francisco, California to Andover, Massachusetts – Transcontinental Double-Rate Postal Cover Via Steamship. Historical Narrative & Postal History Context. This historic transcontinental cover was mailed from San Francisco in January 1858 and sent via the Panama route to Miss Emma L. Horwell at the historic Abbott Female Seminary (Abbot Academy) in Andover, Massachusetts. On January 5, 1858. She arrived at the. And hauled across the Isthmus to. Where it was distributed to the rail lines heading north to Andover, Massachusetts. Postal Rates & Philatelic Details. 20 cents, representing a scarce transcontinental. (2 × 10¢ per 1/2 ounce for distances exceeding 3,000 miles) under the U. Features a slightly overlapped pair of 10-cent green George Washington perforated issues (Scott #32 or #33). Both stamps boast intact perforations and very strong, well-centered designs. Faint but legible black San Francisco, Cal. Town cancel overlapping the stamps and envelope. “San”, “Cal”, “Jan”, and the “18” of the year date are clearly discernible. The upper-left corner features contemporary era handwriting identifying the vessel. Extremely clean presentation with excellent eye appeal. The stamp pair is beautifully positioned with clear margins and intact perforations. The cover is open and. Missing its back flap. The reverse features light, vintage pencil docketing from previous philatelic collections/dealers, reading. “Type 3 double rates”.