In 1811 he began publishing trade directories for Manchester, competing with the firm of R. & W. Dean but later joining with them in 1815 to produce Pigot & Dean's Manchester and Salford Directory.
[1] He began publishing The Commercial Directory in 1814, and expanded to other cities, including London in 1823.
His company stopped producing directories for London and the Home Counties after 1840 in the face of fierce competition from the firm of Kelly & Co. Pigot died in 1843, and Slater continued publishing directories on his own (after 1852 only for northern England, Scotland, and Ireland).
After Slater's own death in 1883, the company was bought by Kelly & Co. in 1892.
[1] Pigot is buried in St. John's Church, Deansgate, Manchester (without an epitaph).