KAMMA
The most influential community in Andhra Pradesh today is the Kamma, or Chowdhary community.
In a numerical ranking (by population size) they would probably be fifth or sixth, but they are concentrated in some areas like Krishna, Guntur, Southern parts of the Godavari river delta, Nizamabad in Telangana and some places of Rayalseema like Anantapur.

Roots of the Kammas:

1. The early "kamma" section could be immigrants into these parts later than 100 AD, probably part of the great kaambhoja migrations from central asia along with the Saka Pallavas who clashed and ultimately merged with the Satavahanas. It has to be remembered the caste thing was not rigid then: Buddhism was prevalent. The pallavas
settled in Guntur-Nellore areas. (for further details, read the inscriptions of  the early pallavas).

2. The next stream seem to be from Northern Uttar Pradesh/Haryana area, during the period when large parts of Andhra pradesh region were coming under the plough for the first time. Forests used to be cleared, a frontier outpost was built round a small temple, the "agraharam" village was given by the kings to brahmins imported from far away lands.  Their job was to popularise agriculture in the area to the hunting and food gathering peoples.
In several places the so called backward tribals picked up education very rapidly and intermarried too. According to one theory Kammas are descended from the foreign immigrant aryas (i.e. brahmins and the warriors and the other people who had a patriarchal system) and the local independent minded tribal warrior girls following a 'matriarchal' social pattern, where women are important and not the men : the head of household is the woman's
brother, while the husband is still considered to be of another clan. This is possible, for the later Kammas maintained a military connection and the girls are still of independent mind.

3. Another theory is that kammas are one of the buddhist era trading communities who regularly travelled between krishna delta and Uttarapatha via Gujarat Rajasthan ( Malwa) and Haryana. There were several well-established and powerful trade guilds and castes.

All these might be correct, but the evidence is indirect and we have little concrete direct proof. So one can't take these as hard proven facts.

The term Chowdhary refers to tax collection of a fourth of the farm produce. While it was said to be introduced during maratha times, it seems to have become fairly popular all over India, and we find "choudharies" in haryana and bengal as well. But it was a revenue post, and sometimes the head of the local merchants' and traders'
guild is also called chowdhary. Possibly the kammas took up trade and business, as explained.

In coastal Andhra area, with the English development of the river Canal system, the river delta Kammas turned to capitalist farming (compared to small scale peasant farming earlier) and other businesses. They run huge sugar, chemical and cement factories, the film industry, cultural institutions, newspapers, etc.

In the Krishna district kammas were active in the struggle against feudal (kamma) landlords and several joined the Communist party. The kammas fully backed the struggle against the feudal Nizam and several gave their lives, too. (The top leadership and backers of the Telugu Desam party are Kamma, claims to the contrary not to be believed. It is true the TDP today is bascially a party of the "backward castes" ie small farmers, though.).