Street numbering
Before the late 1830s
Until the 1830s, the streets of Oxford had no organized numbering system. This was true of most streets in England that had grown organically; the only houses to have numbers before the 1830s were likely to be in terraces (as in Bath) that were built completely afresh.
People would thus find their way by directions such as "Two doors to the right of the Angel". This would have worked well in central Oxford, as its old streets were punctuated at regular intervals not only by shops, and inns and pubs, but by colleges and university buildings.
Late 1830s to mid-1880s
Robson's Commercial Directory of 1839 is the first directory of Oxford to show numbered houses, and the inauguration of the Penny Post the following year precipitated the almost universal numbering of city streets in England. (Villages managed without numbers until the 1920s, however, and many houses in the country continued with house-names instead of numbers until the 1960s.)
From the 1830s to the mid-1880s, houses were numbered continuously, with 1, 2, 3 etc. from the main junction of a street to the end, with the numbering being picked up on the other side of the road and continuing back to the starting end. This meanst that the lowest and highest numbers would always be opposite each other: for instance, in Oxford's High Street, Lloyd's Bank at No. 1 faces the Edinburgh Wool Mill shop at No 143.
Most of the pre-1880 streets of Oxford are still burdened with this old numbering system, which makes it impossible to estimate which side of the road a higher number will fall.
Hunt's Oxford Directory for 1846 shows that most of the streets of central Oxford had the same numbers then as they do today, give or take a bit of infilling. Besides the High, the other Oxford streets which still have this old-fashioned numbering system include Beaumont Street, Broad Street, Cornmarket Street, King Edward Street, Magdalen Street, New Road, Pembroke Street, Queen Street, St Giles, and Turl Street, as well as most of the streets of the old dense suburbs of East Oxford and Jericho (including Walton Street itself).
1880s to present
In the 1880s, a new, more sensible, method of numbering new houses was implemented, putting odd numbers on one side of the road and even numbers on the other (starting with the lowest numbers at the main junction of the road). This means that without any prior knowledge whatsoever, anyone can deduce from a map where a number will fall in a street.
The odd numbers tend to be on the north side of a street with an east–west axis, and on the east side of a street with a north–south axis.
When the odds and evens system was introduced, it was primarily just used in Oxford for newly built streets (e.g. Boulter Street, Marlborough Road, and Walton Well Road). A few roads which had not had time to settle into the old numbering system were renumbered (e.g. Plantation Road and Catherine Street by 1887, and Norham Gardens by 1889), but on the whole the numbering of the old streets was left in the old consecutive system.
When old streets which formerly only had house-names and no numbers (such as the Woodstock and Banbury Roads) were given rational numbers for the first time in the 1880s, the new system was of course used from the start.
Other streets which once had widely spaced houses with swathes of spare land have been subject to so much infilling that renumbering became essential between the 1930s and the 1950s. Thus the Marston Road (greatly infilled) has the modern style of numbering, while Marston Street (where the houses are terraced and could not be breached) the old. And in central Oxford, George Street was renumbered in 1895/6 when the building of the Old Fire Station and the Corn Exchange knocked a hole in the old numbering system.
As for the outlying villages that became suburbs of Oxford in the twentieth century, numbering there was treated summarily by the city. When Headington and Cowley became part of Oxford in 1929, their old-fashioned numbering system was generally modernized in one fell swoop.