The black vote - playing a bigger role in elections across South

Early farmers in this region found the soil infertile. But in the 1840s an English geologist noted that there were limestone, coal, and iron deposits here that might one day make this an industrial center.

He was right. In time, Birmingham became a steel town, more akin to the smokestack cities of the Northeast than to many of its Southern sisters. The city's early white leaders often addressed one another as ''colonel'' and ''regarded the mayor's office as their private domain,'' historian Virginia Van der Veer Hamilton notes.

Today, steel, which until recently was the No. 1 source of jobs here, has been replaced by the University of Alabama, with its large medical faculty and hospital complex. And the man in the mayor's chair is black, elected almost entirely by other blacks.

In fact, Birmingham and Alabama in general offer some insights on the extent of the growing black political clout in the South and in other parts of the nation today. That clout is having a major effect on this year's presidential campaign.

Blacks now account for nearly 30 percent of the registered voters in Alabama. But only two candidates - Democrats Jesse Jackson and Walter Mondale - are likely to get much of the black vote. They are both working hard to get as much of it as they can.

The quest for black votes is still a relatively new phenomenon in the South, although the focus on blacks is not. In his classic book, ''Southern Politics,'' published in 1949, V. O. Key Jr. wrote: ''In its grand outlines the politics of the South revolves around the position of the Negro.'' But the whole South was not preoccupied with controlling blacks; it was primarily whites in counties with the highest black population who were most concerned with that control, he notes. These counties became known as the ''black belt'' areas, though the name had originally stemmed from the rich black soil.

''What V. O. Key talked about was true,'' says Joe Reed, whom many describe as the most politically powerful black in the state. But those days are over, he says. Today there are two black state senators from the heart of Alabama's black belt, for example.

And statewide, white candidates have been forced to recognize the increasing black clout on election day, he says. Mr. Reed heads the Alabama Democratic Conference, is the No. 2 man in the state's powerful educational lobby organization, and is vice-chairman of the state Democratic Party. The ADC endorses candidates - blacks or else whites sympathetic to black interests, he says. The ADC endorsed Mr. Mondale over Mr. Jackson, Reed says, because Mondale has a more ''realistic'' chance of beating President Reagan.

Although the ADC supported George C. Wallace in his successful bid to regain the governor's chair in 1982, it did so only after supporting another candidate in the primary. Today, Reed gives Mr. Wallace a ''passing mark,'' but adds that he is ''not satisfied'' with Wallace's performance.

Many blacks in Alabama are rebelling against what some call Reed's dictatorial methods in the ADC. And black support for the Rev. Mr. Jackson is strong, despite the ADC support for Mondale. Lowndes County Sheriff John Hulet, a black, is urging that the ADC's screening process prior to endorsements be made more open and public.

The ADC is ''not that democratic,'' says state Sen. J. Richard Pearson, a black from Birmingham. But he adds, ''If we didn't have it, we (blacks) would be 50 years behind.''

Mr. Pearson's own view of Wallace today is that the governor has shown no real signs of a change of heart concerning blacks. The governor has long since laid aside racial remarks but, according to Pearson, has not acted to help blacks on key issues. And white pressure against state legislators who even begin to support measures aimed at helping blacks remains intense. Such a legislator is likely to get calls from angry whites in his home county even while debate is under way on the floor of the Legislature.

Birmingham Mayor Richard Arrington, the city's first black mayor, now in his second term, criticizes Wallace for filling two recent state court vacancies here with whites. ''It's that kind of thing that makes you wonder'' whether Wallace has changed or not, he says.

He explains his personal support of Mondale by saying he feels the former vice-president needs to win as big as possible in the primaries to be as strong as possible against Reagan in November. As for his own presence in office, he says it's another ''manifestation of the growing black political clout'' in Alabama. Fifty-one percent of the city's voters are black, he says.

The Rev. Abraham Woods Jr., who aided in a draft-Arrington effort after a white policeman shot and killed an unarmed black here, is supporting Jackson, however. ''I had to follow my heart; I'm following a dream,'' he explains at his church's day-care center. In his lapel is a Jackson button. On one wall is a painting of the late Dr. Martin Luther King Jr. ''If we're ever going to make the White House, we've got to make a start,'' he says.

But while many whites are not used to seeing a black run for president, neither are they used to voting for a black for mayor. Few whites have voted for Arrington. The mayor says he hopes whites, as part of a ''maturation process,'' will learn to support some black candidates. He says he has worked for blacks and whites, launching, for example, not only low- but moderate- and middle-income housing programs. He also cites a drop in crime and police brutality.

But many whites remain alienated from the city and its mayor, says Frank Parsons, a white lawyer who in 1979 barely lost to Mr. Arrington. Some whites are still leaving the city, some businesses are moving out, and the mayor is ''missing opportunities'' to make better ties with the business community, Mr. Parsons says. The mayor says those ties are strong.

''There are a lot of white folks around who don't like black folks,'' especially among the older generations, Parsons says.

But gone are the days of police with dogs attacking marching blacks, and the bombing of black churches - gone forever, it is hoped.

''Birmingham of the 1980s is not the Birmingham of the 1960s,'' says Odessa Woolfolk, director of the Center for Urban Affairs at the University of Alabama in Birmingham.

Nor is the South of the 1980s the same as the South of the 1960s.