They say you never know where you're going until you know where you're coming from. Here's a rundown of what was happening in the hip-hop world while your parents were still in diapers.
I first wrote this for About.com but I'm going to make weekly (or monthly) installations here as well, with little alterations. Now, no one's claiming this to be the hip-hop gospel. So, if you find that some notable events are missing from the timeline, feel free to point them out. Major props to Davey D for posting up the full version on his site. It took me an awful long time to compile.

Here we go:

Hip-Hop Timeline 1925 - 1975

1925: Earl Tucker (aka Snake Hips), a performer at the Cotton Club invents a dance style similar to today’s hip-hop dance moves including floats and slides. Similar moves would later inspire an element of hip-hop culture known as breakdancing.

1940: Tom the Great (Thomas Wong) uses a booming sound system to please the crowd. Wong also used American records to swindle music-lovers from local bands.

1950: The Soundclash contest between Coxsone Dodd’s “Downbeat” and Duke Reid’s “Trojan” gives birth to DJ Battling.

1956: Clive Campbell is born in Kingston, Jamaica. Campbell would later become the father of hip-hop.

1959: Parks Commissioner Robert Moses starts building an expressway in the Bronx. Consequently, middle class Germans, Irish, Italians, and Jewish neighborhoods disappear in no time. Businesses relocate away from the borough only to be replaced by impoverished black and Hispanic families. Along with these poor people came addiction, crime, gang-related activities, and unemployment.

1962: James Brown records Live At The Apollo. Brown’s drummer Clayton Fillyau popularizes a sound that is now known as the break beat. The break beat would later inspire the b-boy movement, as breakers danced to these beats at block parties.

1965: In a historic boxing bout, Muhammad Ali (born Cassius Clay) defeats Sonny Liston in the 6th round. Before the bout, however, Ali recited one of the earliest known rhymes:

Clay comes out to meet Liston
And Liston starts to retreat
If Liston goes back any further
He'll end up in a ringside seat.
Clay swings with a left,
Clay swings with a right,
Look at young Cassius
Carry the fight.
Liston keeps backing
But there's not enough room
It's a matter of time...

1967: Clive Campbell migrates to the United States at the age of 11. He would later become a graff writer and change his name to Clyde As Kool. Because of his size, kids at Alfred E. Smith High School nicknamed him Hercules. He didn't like the name so he decided to go with the shortened form, Herc. Herc later became Kool Herc, a renowned hip-hop DJ that would help inspire a global culture.

1968: A gang named Savage Seven would hit the streets of the East Bronx. Savage Seven later transforms into Black Spades, before eventually becoming an organization known as Zulu Nation.

1969: James Brown records two songs that would further influence the drum programming in today’s rap – “Sex Machines” with John Starks playing the drums and “Funky Drummer” with Clyde Stubblefield on the drums.

1970: DJ U-Roy invades Jamaican pop chart with three top ten songs using a style referred to as toasting. The Last Poets release their self-titled debut album on Douglas Records combining jazz instrumentations with heartfelt spoken word. (The Last Poets were featured on Common’s 2005 rap anthem, “The Corner").

1971: Aretha Franklin records a well-known b-boy song “Rock Steady.” The Rock Steady Crew would go on to rule in the world of break-dancing, with members all across the globe.

1972: The Black Messengers (a group that staged performances for The Black Panthers and rallies relating to the black power movement) feature on The Gong Show.
However, they are only allowed to perform under the alias “Mechanical Devices,” because of their controversial name.

1973: DJ Kool Herc throws his first block party at 1520 Sedgwick Avenue, Bronx, NY. Herc would often buy two copies of a record and stretch the break parts by using two turntables and mixing in both records before the break ends. The Zulu Nation is officially formed by a student of Stevenson High school named Kahyan Asim (aka Afrika Bambaataa).

1974: After seeing Kool Herc perform at block parties, Grandmaster Caz, Grandmaster Flash, and Afrika Bambaataa start playing at parties all over the Bronx neighborhoods. Around this time, DJ/MC/Crowd Pleaser Lovebug Starski starts referring to this culture as “hip-hop."

1975: [Herc is hired as a DJ at the Hevalo Club. He later gets Coke La Rock to spit crowd pleaser rhymes at parties (e.g.“DJ Henry is in the house and he'll turn it out without a doubt”). Coke La Rock and Clark Kent form the first emcee team known as Kool Herc & The Herculoids. DJ Grand Wizard Theodore invents ‘the scratch’ by accident. Legend has it that while trying to hold a spinning record in place in order to listen to his mom, Grand Wizard accidentally caused the record to produce the “shigi-shigi” sound that is now known as the scratch.

Part 2 next week...