Alterswil was first mentioned in 858 as Altiricheswilae, Oberglatt in 731 as villa Clata and in 1316 as Obren Glat and Burgau in 964 as Purchouva.

Of the rest of the land, 23% is settled (buildings or roads) and the remainder (1.3%) is non-productive (rivers or lakes).

It consists of the extended linear village of Flawil and the hamlets of Botsberg, Alterswil, Grobenentschwil, Langenentschwil, Raschberg, Egg, Oberglatt and Burgau as well as scattered farm houses.

The blazon of the municipal coat of arms is Chequy Argent and Gules and a Chief Or.

Of the foreign population, (as of 2000[update]), 138 are from Germany, 516 are from Italy, 964 are from ex-Yugoslavia, 64 are from Austria, 138 are from Turkey, and 516 are from another country.

[8] The age distribution, as of 2000[update], in Flawil is; 1,216 children or 13.0% of the population are between 0 and 9 years old and 1,248 teenagers or 13.4% are between 10 and 19.

The next access to the A1 national motorway are located in neighbouring towns Gossau and Uzwil The Old Town Council building German: Altes Rathaus in Burgau and the Hotel-Restaurant Hirschen German: Gasthof Hirschen in Oberglatt are listed as Swiss heritage sites of national significance.

[9] The hamlets of Burgau, Raaschberg and Oberglatt are designated as part of the Inventory of Swiss Heritage Sites.

Further industrial firms include FLAWA AG, producing cotton wool products and bandage material, SFS intec AG, specialised in deep drawing and impact extrusion, and BÜCHI Laboratory Equipment.

From the 2000 census[update], 4,295 or 46.1% are Roman Catholic, while 2,755 or 29.6% belonged to the Swiss Reformed Church.

The wettest month is August during which time Flawil receives an average of 149 mm (5.9 in) of rain or snow.

The driest month of the year is October with an average of 76 mm (3.0 in) of precipitation over 13.3 days.