If so what were the reason for the opposition?
I'll speak about Alaska's situation.
Yes, and the reasons for it are fascinating.
Imagine you're a Southern Democratic U.S. Senator in 1956. You're facing pressure to end segregation and pass some sort of civil rights legislation. If you do, you'll be voted out of office in a second. If you don't, you risk being marginalized in your own party. Fortunately, you're in a good position — the U.S. Senate hasn't passed a civil rights bill since the 1870s, and it doesn't seem likely to.
If Alaska and Hawaii enter the Union, that could change the balance of power in the Senate. You hardline Southern Democrats are a minority, but the other Democrats know that if they want to stay in power, they need you. Your friends are people like Rep. Howard Smith (Democrat, Virginia). “I want to keep the United States of America on the American continent,” he said on the House floor in 1955.
The House passes a statehood bill for Alaska and Hawaii, but you're not budging in the Senate. You like the way things are. Besides, you argue, Alaska is too cold and remote and can't support itself economically. It's practically a ward of the federal government.
Unfortunately for you, Lyndon Johnson is thinking about running for president in 1960. He needs to burnish his civil rights credentials if he wants to win northern voters. Instead of thinking Southern, he starts casting himself as a Western progressive. With Johnson in play, things start to shift. He's a wheeler and dealer, and he has powerful friends. He gets the Civil Rights Act of 1957 through the Senate, and although it's toothless, it's a sign of changing times.
That same year, oil drillers make a big strike on the Swanson River in southern Alaska. Pretty soon, there's not much ground to stand on when it comes to saying that Alaska can't support itself. Making matters worse for you, those pesky Alaskans are pretty good lobbyists. There's the territory's two newspaper publishers, a bunch of young politicians — including that lawyer, Theodore Fulton Stevens — and Fred Seaton, Eisenhower's Secretary of the Interior.
Alaskans have already voted 6-1 in favor of statehood and created a constitution to boot.
In 1958, when Johnson sets up the vote on Alaska/Hawaii statehood in the Senate, there's little point in standing in the way — though clever old Johnson has the sense to stay out of town when the vote sails through the Senate, 64-20.
Sen. Strom Thurmond (South Carolina, Democrat) still does his best, outlining six reasons to reject statehood. The fifth is particularly interesting: "The admission of Alaska, a noncontiguous area, would set a precedent for the admission of other noncontiguous areas, whose customs, traditions, and basic philosophies have non‐American roots."
In Alaska, there's wild celebrations. Down in Seattle, they're gnashing their teeth — Alaska statehood will mean an end to fish traps, the low-maintenance way for canneries to catch millions of salmon. Most Alaskans hate them, since the canneries (mostly owned by Outside interests) own the traps and thus catch all the fish. There's a few Alaskans tied to the fish traps, but they're vastly outnumbered.
What about Alaska Natives, you ask?
You're in luck. As part of the 50th anniversary of Alaska statehood, this question was answered in detail in Alaska Native Perspectives of Statehood, which Sealaska Heritage Institute hasn't yet sent to press.
Initially, statehood was viewed extremely positively by most Natives, particularly those who fished for a living. That's because the new state almost immediately banned fish traps. These were large, fixed structures erected just offshore near major salmon-producing rivers. Each year, they'd catch tens of thousands of fish for canneries.
Trouble was, these traps were owned by huge companies, all of which were based in places like Seattle or San Francisco. They competed with Alaskan fishermen and were hated.
Statehood promised the elimination of fish traps, and it carried through. "I was 4 at statehood. I remember growing up after statehood and my father speaking of the big celebrations and parties since we were doing away with fish traps. They were happy," said University of Alaska Anchorage professor Jeane Breinig.
Breinig is the lead researcher on this topic:
... she discovered that historical records showed most Southeast Alaska Natives generally supported statehood, but only tepidly and if conditions for statehood favored — and didn’t hurt — Native land claims, subsistence rights, and other important aspects. Southeast Alaska Natives, through Alaska Native Brotherhood and Sisterhood’s efforts, the work of their lawyers William L. Paul Sr. and Jr., and the ANB attorney James E. Curry, had previously fought against some statehood bills that attempted to deprive Alaska Natives of land, most notably in 1950, but they did cautiously go along with the 1959 statehood bill — though most clearly had hoped statehood would have brought more to Alaska Natives ...
Statehood also promised land reform and the restoration of Native land rights. This didn't happen until the Alaska Native Claims Settlement Act in the 1970s, and ANCSA remains a controversial topic. Some say it worked, some say it didn't.
KNBA-FM did a great oral history a few years ago, collecting some stories on this issue. If you have the time (they're only 30 minutes each), part 1 is here and part 2 is here.
If you have a bit more time, here's a 47-minute lecture by Breining on this very topic.
For a complete history of the statehood struggle, I recommend Fighting for the 49th Star: C.W. Snedden and the Crusade for Alaska Statehood.