Chiba Urban Monorail Line 1

Like the rest of the network, Line 1 is built to the Mitsubishi SAFEGE design, a suspended type in which the cars hang beneath a single hollow concrete beam with the running surfaces and bogies enclosed inside it, shielding the moving parts from rain, snow and ice. Mitsubishi Heavy Industries had built and tested two earlier suspended SAFEGE monorails — the Higashiyama Park Monorail and the Shōnan Monorail — before drawing on that experience to construct the larger Chiba system, which remains the world's only dual-beamed SAFEGE-type network. Chiba officials chose the design partly because the slim overhead beam threads above existing city streets and because the enclosed structure copes with the region's occasionally inclement weather. On Line 1 the trains run at up to 45 km/h over gradients as steep as 44 per mille and curves as tight as a 50-metre radius.

Line 1 was the second of the company's two routes to begin operating, opening after Line 2 had already been running for several years. Its first section, between Chiba-Minato Station and Chiba Station, entered service on 1 August 1995 and at first through-ran with Line 2 as a single operating system reaching Chishirodai. This inner stretch links the Chiba-Minato waterfront, where roughly half the route crosses reclaimed land along Tokyo Bay, with the city centre, and it provides the monorail's interchange with the JR Keiyō Line; in practice it functions as an extension of Line 2 toward the bay.

The line was completed on 24 March 1999, when the section from Chiba Station onward to Kenchō-mae Station opened and Line 1 reached its full 3.2-kilometre length. With the whole monorail now finished, the two routes were reorganised into separate operating systems: from this point Line 1 trains served the Kenchō-mae direction, while Line 2 reverted mainly to self-contained running, only a few trains in the weekday morning peak continuing onto the Chiba-Minato section. The same 1999 changes cut Line 2 running times by about a tenth and equipped every station with automatic fare-adjustment machines.

Through-operation between the two lines was restored on 1 December 2002, after Keiyō Line rapid trains began stopping at Chiba-Minato Station all day; from then almost all Line 2 services ran onto the Chiba-Minato section, strengthening transfer-free access from the Line 2 corridor to the Keiyō Line. Both lines' trains have continued to share the Chiba-Minato–Chiba inner stretch ever since, running about nine times an hour through the middle of the day.

The Chiba–Kenchō-mae portion, which threads through the city's largest shopping district toward the prefectural government offices at Kenchō-mae, has always been lightly used because it lies close to several other railway stations. Service there has been pared back over time: from an initial daytime frequency of one train every ten minutes it was widened to every twelve minutes in December 2002 and then settled at a train every fifteen minutes all day from 15 March 2008, with the once-heavy weekday morning peak greatly reduced. Across the wider network, the combined 15.2-kilometre system — of which Line 1 contributes 3.2 kilometres and Line 2 the remaining 12.0 — was certified by Guinness World Records in 2001 as the world's longest suspended monorail.

Several eastward extensions of Line 1 beyond Kenchō-mae were studied over the years, principally a link to Chiba Municipal Aoba Hospital, but they were repeatedly scaled back and frozen amid weak ridership and fiscal constraints, and on 4 September 2019 Chiba City announced that the hospital-route extension plan had been abolished. In its later years the line was modernised in step with the rest of the system: the Type 0 "Urban Flyer" trains entered service from 2012, the operator announced network-wide station numbering on 20 February 2019, and on 31 August 2019 the line's first platform fences were installed at its busiest stop, Chiba Station.

• 197920 March: Chiba Urban Monorail Co., Ltd. is established as a third-sector company funded by Chiba City and Chiba Prefecture.
• 198229 January: groundbreaking ceremony for the monorail is held.
• 19951 August: Line 1 opens between Chiba-Minato Station and Chiba Station; it through-runs with Line 2 toward Chishirodai as a single operating system.
• 199924 March: the Chiba–Kenchō-mae section opens, completing Line 1 at 3.2 km; the two routes are separated into distinct operating systems and Line 2 running times are cut by about 10% with automatic fare-adjustment machines installed at all stations.
• 20021 December: through-operation between Line 1 and Line 2 is resumed after Keiyō Line rapid trains begin stopping at Chiba-Minato all day; the daytime interval on the Chiba–Kenchō-mae section is widened from 10 to 12 minutes.
• 200621 June: a Line 2 train collides with the arm of a crane truck doing sewer work between Sakusabe and Chiba-Kōen stations.
• 200815 March: the Chiba–Kenchō-mae section moves to an all-day 15-minute interval.
• 20128 July: the new Type 0 "Urban Flyer" trains enter service.
• 201920 February: the operator announces the introduction of station numbering across the network ahead of the 2020 Tokyo Olympics and Paralympics.
• 201931 August: the line's first platform fences (fixed barriers) are installed at Chiba Station.
• 20194 September: Chiba City announces that the planned Kenchō-mae–Aoba Hospital extension of Line 1 has been abolished.