A: London, England, United Kingdom
Until the development and widespread adoption of the electric telegraph, letter writing was the only way to communicate with people at a distance, and because of the high cost of telegraph, until the invention of the telephone, and later of email, letter writing remained the primary method. However, prior to 1840 sending a letter could cost as much as a day's wage for the working classes, and those receiving a letter had to pay for its delivery. Prepayment was also social slur on the recipient; one had to be financially solvent to receive a letter. If the recipient could not afford to pay for a letter, it was returned to sender. Thus for the working classes, leaving home often meant losing touch with family and friends.
In 1837 English teacher, inventor and social reformer Rowland Hill circulated his privately printed pamphlet, Post Office Reform: its Importance and Practicability. In this Hill explained why the postal system needed reform, and laid out his principles for reform. It may be validly argued that Hill's invention of the Penny Post was the greatest stimulus to written communication in history, making written communication affordable to all classes of society.
"The penny post inaugurated and administered by Rowland Hill required the adoption of four novel principles: (1) prepayment of postage, (2) payment by weight instead of by the number of sheets, (3) the use of envelope, (4) the use of adhesive stamps on letters. Prior to this reform, for example, the use of an envelope would have been a novelty to most letter-writers and entailed double postage" (Carter & Muir, Printing and the Mind of Man  306a).
"In the 1830s, charges were notoriously inconsistent since the Post Office determined single, double, or triple rates according to the number of miles a letter traversed to get to its destination and the number of sheets of paper (and enclosures) a writer used. A letter might not necessarily travel the most direct or economical route. In addition, postal workers used “candling” — an inexact method of holding a letter up to the light — to assess the number of letter sheets or enclosures. Any reader of Jane Austen’s Emma (1815) knows that to save costs, cross writing was common — a writer turned his or her letter horizontally and “crossed” (or wrote over) the original text at a right angle rather than use an additional sheet of paper. Folded letters with a wax seal may look quaint, but like cross writing, this was also a pre-1840s cost cutting measure since that same missive, posted in an envelope, would receive double charge."
"One of the first things Queen Victoria did when she came to the throne in 1837 was to appoint a Select Committee on Postage, chaired by Robert Wallace MP and charged to look into the condition of the post with a view towards postal rate reduction. Victoria, on August 17, 1839, gave royal assent to the Postage Duties Bill and, in 1840, ushered in Uniform Penny Postage and the enormously popular adhesive postage stamp, prepaid by the sender (an unpaid letter cost the recipient 2 pence to encourage prepayment). The Penny Post abolished the much-abused system of franking — postmarks granting Members of Parliament and the Queen free carriage of mail — and transformed the mail from an expensive tax for revenue to a civic service affordable to all social classes" (http://www.victorianweb.org/technology/letters/intro.html, accessed 04-17-2013).