Between 1910 and 1930, the growth of the city generated many new extensions to the tram lines.
The first thirteen electrified tram lines were joined by: line 14 in 1910, lines 15–18 in 1913, line 19 in 1916, lines 22 and 23 in 1921, line 20 in 1922, line 21 in 1928, line 24 in 1929 and line 25 in 1930.

In 1931, the tramway network reached its greatest extent, at 25 tram lines.
From that year to 1940, (almost) all the districts in the city could be reached by tram.
Between 1900 and 1930, the fleet grew to 445 motorised trams and approximately 350 trailers.
These were all twin axle vehicles with wooden bodies.

From 1922 until 1971, all trams had mailboxes at their rear side.
These were emptied at Centraal Station; the post office's distribution centre was located next to the station, at Stationsplein, and later at Oosterdokskade.
Thanks to the tram mailboxes, a letter could be delivered on time, even if it is too late for the last collection from the regular mailboxes.

During the Great Depression of the 1930s, the tram service was reduced.
In 1932, lines 12, 15, 19, 20 and 21 were abandoned.
However, as part of the Eastern Railway Works (Spoorwegwerken Oost) in 1939-1942, trams came to the new neighborhoods in Amsterdam-Oost, to serve the Watergraafsmeer, the new Amstel station and the rebuilt Muiderpoort station.

On 1 January 1943, the GTA merged with the Gemeenteveren to form Gemeentelijk Vervoerbedrijf (GVB).

Between 1940 and 1945, the trams carried big crowds and faced a crisis.
Several lines had to be suspended (lines 4, 6, 8 and 14), before the whole service ceased in October 1944 due to a coal shortage.
Many tram cars were transported eastward.
Between 1910 and 1930, the growth of the city generated many new extensions to the tram lines. The first thirteen electrified tram lines were joined by: line 14 in 1910, lines 15–18 in 1913, line 19 in 1916, lines 22 and 23 in 1921, line 20 in 1922, line 21 in 1928, line 24 in 1929 and line 25 in 1930.
In 1931, the tramway network reached its greatest extent, at 25 tram lines. From that year to 1940, (almost) all the districts in the city could be reached by tram. Between 1900 and 1930, the fleet grew to 445 motorised trams and approximately 350 trailers. These were all twin axle vehicles with wooden bodies.
From 1922 until 1971, all trams had mailboxes at their rear side. These were emptied at Centraal Station; the post office's distribution centre was located next to the station, at Stationsplein, and later at Oosterdokskade. Thanks to the tram mailboxes, a letter could be delivered on time, even if it is too late for the last collection from the regular mailboxes.
During the Great Depression of the 1930s, the tram service was reduced. In 1932, lines 12, 15, 19, 20 and 21 were abandoned. However, as part of the Eastern Railway Works (Spoorwegwerken Oost) in 1939-1942, trams came to the new neighborhoods in Amsterdam-Oost, to serve the Watergraafsmeer, the new Amstel station and the rebuilt Muiderpoort station.
On 1 January 1943, the GTA merged with the Gemeenteveren to form Gemeentelijk Vervoerbedrijf (GVB).
Between 1940 and 1945, the trams carried big crowds and faced a crisis. Several lines had to be suspended (lines 4, 6, 8 and 14), before the whole service ceased in October 1944 due to a coal shortage. Many tram cars were transported eastward.
Trams in Amsterdam