Tim Gilbert said:

Gons can be roughly split into three groups based on their bottoms:

1)

solid; 2) side drop; and 3) center drop.

According to the April 1949 ORER, there were 305,501 gons. The table
below splits this geographically by type of bottom (in thousands):

EAST SOUTH WEST TOTAL
Solid Bottom 142 32 31 205
Side Drop 2 7 62 71
Center Drop 3 25 1 29
Total 147 64 94 306

Tony Thompson stated:

Something's fishy about this table, unless the usual GS (AAR class)
gondola is considered a "side drop;" SP alone had over 5000 GS gons in
1949. Thus I would suppose that "center drop" means between the rails
only,
not GS class.

Per page 781 of the April 1949 ORER,

" 'GS' - An Open Top Car, having fixed sides and ends and drop bottom,
consisting of doors hinged at the center sills to dump outside of
rails."

There were listed in the April 1949 ORER 62,488 side dump gons owned by
the western roads of which 7,908 were owned by SP's Pacific Lines. Where
is the fish?

Tim Gilbert