NORTH FORK, Idaho (AP) _ A bit of Americana slipped into history Thursday when the nation's last known operating hand-cranked, party-line telephone system was disconnected - replaced by private-line, touch-tone technology.

''Now that I know it's working, I'm going to call my mother back in Iowa,'' said Joyce Rinehart at the Ramshead motel and restaurant. ''This is the first time I've talked on a phone like this in a long time where I could hear and not have to shout.''

''I'm not screaming anymore,'' said Garry Pedrow as he answered the first incoming call on the new system at his Shoup Country Store near North Fork in central Idaho's rugged Salmon River canyon. ''It's sure nice.''

The depression-era, single-line, ring-down system, a fixture of rural America in decades past, had been the link to the rest of the world for the 18 year-round canyon residents.

Parties on the line could crank the magneto to ring others along the line or the central office for a connection to town numbers and long-distance. Each customer had a coded ring and supposedly answered just that ring while ignoring the rest.

Operator Steve Freestone handled the last outgoing call from the old system at the switchboard of his Motel Deluxe in Salmon 20 miles away and then announced the old line was dead.

A half hour later, state Public Utilities Commission President Joe Miller placed the first call on the new system to Gary Byrne, head of the Rural Electrification Administration, which underwrote the $350,000 modernization.

''We're moving into our second century,'' said Miller, referring to Idaho's centennial on July 3. ''It's time for as much of our state as possible to be connected to the rest of the world in a meaningful way.''

The demise of the battery and magneto system was set a year ago when AT&T said computerization would require the elimination of the local operator.

Freestone and the operators preceding him connected calls from canyon customers to the proper numbers outside and routed incoming calls to the right phone, using a series of coded rings. The Shoup Country Store was three longs.

AT&T, US WEST and Century Telephone Co. in Salmon agreed to keep the operator in place until installation of the new system.

Residents along the wilderness river had mixed feelings about losing a system they felt fit in well with a lifestyle that includes only seasonal running water and requires private generators for electricity.

''It's historic, ... but when you're in business you need a town phone system,'' said Rinehart at the Ramshead motel and restaurant about 30 miles down the canyon.

The crank system was originally set up by the U.S. Forest Service in 1931. It was bought by the resident cooperative called the North Fork Telephone Corp. for a dollar in 1952 when the government switched to radio communications. The years had taken their toll.

''It's a raggedy old thing,'' Freestone said. ''They've got it nailed to trees and mountains. Most of the time you have to yell pretty loud to talk to people down river.''

In their heyday, the wall-mounted units with a black metal mouthpiece on an arm and a receiver hung on a two-prong hook on the left side were the communications heart of as many as 1.25 million American farms and ranches.

Party line chatter, with two or three parties talking and several more secretly listening, was a popular rural recreation, long before electricity, television and even radio.

Pedrow said the canyon residents are keeping a few of the hand crank phones hooked together for the historic value, an idea whole-heartedly endorsed by Rinehart.

''I'd just like to keep them around to show the younger generation what we had to use,'' she said. ''On this old system I've talked to the Marshall Islands. I've talked to Canada. I've talked to Hawaii. So that old line did reach out.''