The historical trade, commercial and "post office" directories are a major source of information for the nineteenth and earlier twentieth centuries.They record the names and addresses of people and this helps to refine the search in census returns and birth, death and marriage records.
Directories can sometimes be helpful in dating photographs from the advertisments of the photographers.
 

Middlesbrough Reference library has an excellent selection of local directories from 1822.Many of the original hard copy versions have been microfilmed.
There are two other sources of directory information you'll find useful:

Guide to the National and Provincial Directories of England and Wales, excluding London, published before 1856, by Jane E. Norton. Royal Historical Society, 1950 (RHS Guides and Handbooks No. 5). 016.9420025

Historical Directories http://www.historicaldirectories.org
Historical Directories is produced and owned by the University of Leicester. It is a digital library of local and trade directories for England and Wales, from 1750 to 1919. Within the digital library you'll find high quality reproductions of comparatively rare books, essential tools for research into local and genealogical history. The Historical Directories web site provides national coverage and also integrates material from different institutions into a coherent, and free, online collection. It is relevant to amateur historians, academics, teachers and the general public.
At its most basic level, the project seeks to provide at least one directory, for each segment on depicted on the geographical map for each of the following decades:
1850s
1890s
1910s
Why focus initially on these decades?
 In the 1850s directories began to be published more widely, also providing information at parish level.
The final decade of the nineteenth century, the 1890s, is fascinating in itself. It also leads up to the 1901 census, which has been published online by the Public Record Office.
Immediately after the 1901 census, the 1910s also provide for potentially large audiences due to the current and intense interest in World War I.
 

The Middlesbrough Reference Library also holds a set of local phone books from 1958 to date.
 
 

Download

Directories in the Local Collection
Filename:  Directories in Middlesbrough Local Collection.htm
Description:    Directories are held in print form and on microfilm. On microfilm our holdings span the years 1823 to 1939, with gaps; and in print span the years 1823 to 1973, again with gaps.
Type and size:    html doc size 76.7KB
 
 

Telephone Directories held in Middlesbrough Reference Library
Filename:  Telephone Directories held in Middlesbrough Reference Library.htm
Description:    The Reference Library holds a set of current directories for England, Scotland and Wales. However, only directories with a local content are retained.
Type and size:    html size 24.9KB